Explanation:

If we use B for black (dominant) and b for light brown (recessive):

• Light brown females must be: bb (homozygous recessive, since they show the recessive trait)
• Black male could be either: BB or Bb

Let black = B (dominant), light brown = b (recessive).
Light brown ewes are bb. If the ram were BB, the cross BB × bb → all Bb (black).
If the ram were Bb, you’d get 50% black, 50% brown. Codominance would show mixed/intermediate coats, not all black.

Explanation of Wrong Answers

• The male must be homozygous (BB) to produce only black offspring
• Black must be dominant because Bb offspring are black

Explanation:

The gall bladder stores bile, which helps emulsify fats. Removal affects fat digestion, not carbohydrate absorption or glucose conversion.

Explanation:

Natural selection favors traits that provide survival advantage, such as insecticide resistance in mosquitoes.

Explanation:

Dominance is not about "strength." It's about expression—dominant alleles mask recessive ones in heterozygotes.

Explanation:

Diffusion is passive and does not require ATP, unlike active transport, nerve conduction, or muscle contraction.

Explanation:

mRNA vaccines can be quickly developed and mass-produced without using live pathogens.

Explanation:

Late-stage syphilis (tertiary) affects the brain, heart, and nervous system after many years.

Explanation:

Blood glucose is regulated hormonally (insulin, glucagon), not directly by nerves.

Explanation:

HIV has 3 stages acute infection, latency, and AIDS. Full recovery does not naturally occur.

Explanation:

Smallpox (variola virus) is a double-stranded DNA virus.

Explanation:

Proteins supply essential amino acids which the body cannot synthesize.

Explanation:

Calcium builds bones, and vitamin D aids its absorption.

Explanation:

Emphysema destroys alveolar walls, reducing elasticity and surface area for gas exchange.

Explanation:

Hypothalamus regulates homeostasis, including body temperature.

Explanation:

Hypothalamus senses blood chemistry changes (osmolarity, temperature, glucose).

Explanation:

To conserve heat and return the decreased temperature to normal, body responds by shivering (to generate heat) and vasoconstriction (to reduce heat loss).

Explanation:

The aorta carries oxygen-rich blood from the left ventricle to the body at high pressure.

Explanation:

During contraction of the right ventricle, the tricuspid valve closes to prevent backflow into the right atrium.

Explanation:

Proteins are metabolized in the liver, producing urea, which enters blood via the hepatic vein.

Explanation:

What is Negative Feedback?

• Negative feedback is a regulatory mechanism that counteracts or reverses changes from a set point
• It maintains homeostasis by responding to deviations in opposite directions
• The response always opposes the initial change

How This System Works:

When water concentration in blood falls (initial change):

1. The body detects low water concentration
2. ADH (antidiuretic hormone) is released
3. Kidneys reabsorb more water, producing concentrated urine
4. Water concentration in blood rises (reverses the initial fall)

When water concentration in blood rises (initial change):

1. The body detects high water concentration
2. Less ADH is released
3. Kidneys reabsorb less water, producing dilute urine
4. Water concentration in blood falls (reverses the initial rise)

Explanation of Wrong Answers

A & C only describe unidirectional changes, not the reversing nature

B describes positive feedback (amplifying changes), which is the opposite of what's happening.

Explanation:

Insulin is a protein hormone (large molecule) and cannot pass through the dialysis membrane pores.

Explanation:

Sensory neurons detect the stimulus, relay neurons transmit in the CNS, and motor neurons activate effectors.

Explanation:

Hypothalamus regulates thirst and water balance via ADH secretion.

Explanation:

Motor neurons carry instructions from CNS to muscles or glands.

Explanation:

Non-competitive inhibitors bind to allosteric sites, changing enzyme shape.

Explanation:

DNA backbone is sugar-phosphate (deoxyribose + phosphate) linked by phosphodiester bonds.

Explanation:

Fatty acids undergo beta-oxidation, producing Acetyl-CoA, which enters Krebs cycle.

Explanation:

Darwin proposed natural selection as the driving mechanism of evolution.

Explanation:

The sphenoid bone forms part of the floor and lateral wall of the skull.

Explanation:

Thoracic vertebrae articulate with ribs.

Explanation:

Biceps are flexor muscles; contraction bends the arm.

Explanation:

Understanding Hemophilia Inheritance:

• Hemophilia is an X-linked recessive disorder
• Males have XY chromosomes, females have XX chromosomes
• Males need only one copy of the hemophilia allele to be affected (since they have only one X chromosome)
• Females need two copies to be affected (one on each X chromosome)

Parents' Genotypes:

• Female carrier: X^H X^h (one normal X, one X with hemophilia allele)
• Normal male: X^H Y (normal X, Y chromosome)

Possible Offspring:

• X^H X^H: Normal daughter (25%)
• X^H X^h: Carrier daughter (25%)
• X^H Y: Normal son (25%)
• X^h Y: Hemophilic son (25%)

For Sons Specifically:
Since the question asks about sons, we only consider male offspring:

• X^H Y: Normal son (50% of sons)
• X^h Y: Hemophilic son (50% of sons)

Explanation:

Hemophilia is X-linked recessive. Females need two defective alleles; males only need one.

Explanation:

Recombinant DNA technology is used; the human insulin gene is inserted into bacteria (like E. coli), which then produce insulin on a large scale

Explanation:

Hepatitis B is caused by a double-stranded DNA virus. Others listed are RNA viruses.

Explanation:

HIV attacks helper T-cells (CD4+), weakening immune response.

Explanation:

Active immunity develops when body produces antibodies after natural infection. Vaccination = artificial active, breastfeeding = passive.

Explanation:

B-lymphocytes differentiate into plasma cells, producing antibodies.

Explanation:

Structure of the Placenta:

• The placenta is a specialized organ that develops during pregnancy
• It attaches to the wall of the uterus (usually the upper part)
• The placenta has two sides: the maternal side (attached to the uterine wall) and the fetal side (connected to the baby via the umbilical cord)

Exchange Mechanism:

• At the uterine wall, maternal blood vessels come into very close contact with fetal blood vessels within the placenta
• The exchange happens through structures called chorionic villi - finger-like projections containing fetal blood vessels that extend into pools of maternal blood
• Nutrients, oxygen, antibodies pass from mother to fetus
• Waste products and CO₂ pass from fetus to mother
• Importantly, maternal and fetal blood don't actually mix - exchange occurs across thin membranes

Why not the other options:

• Oviduct (fallopian tube): This is where fertilization occurs, not where the placenta develops
• Cervical wall: The cervix is the lower part of the uterus that opens to the vagina; the placenta doesn't attach here
• Umbilical cord: is the connection between placenta and fetus, but the actual exchange with maternal blood happens where the placenta attaches to the uterine wall

Explanation:

After ovulation, corpus luteum secretes progesterone to prepare endometrium for implantation.

Explanation:

Amniotic fluid cushions and protects fetus.

Explanation:

Vena cava brings deoxygenated blood to right atrium; pulmonary artery carries it to lungs.

Explanation:

Discontinuous variation = distinct categories (e.g., presence/absence of a genetic trait).

Explanation:

Triceps are extensors, they straighten the arm while biceps relax.

Explanation:

A catalyst speeds up reaction but does not shift equilibrium position.

Explanation:

Humerus forms ball-and-socket joint with scapula at shoulder and hinge joint with ulna at elbow.

Explanation:

• Man = 1

• Wives = 5

• Daughters = 7

• Sons = 6

• Sons’ wives = 6

• Sons’ children = 12
  Total = 1 + 5 + 7 + 6 + 6 + 12 = 37

Explanation:

The pattern increases letters by 3 (D→G→J→M), numbers by 1 (1→2→3→4), and letters again by 3 (F→I→L→O).

Explanation:

Football, Tennis, and Hockey are outdoor field games, while Billiards is an indoor table game.

Explanation:

We know Azra > Munir and Javaid > Munir. Both are older than Munir, but there’s no information comparing Azra and Javaid directly—either could be older.

Explanation:

Given information:

• Total players: 50
• Hockey players: 30% of 50 = 15 players
• Cricket players: 80% of 50 = 40 players

Let me use the principle of inclusion-exclusion.
If we add the number of hockey players and cricket players: 15 + 40 = 55 players

But we only have 50 players total! This means we're counting some players twice - those who play both sports.

The minimum number who must play both sports = (15 + 40) - 50
= 5 players

To verify this makes sense:

• Minimum overlap occurs when we maximize the number playing exactly one sport
• If 5 play both, then 10 play only hockey and 35 play only cricket
• Total: 10 + 35 + 5 = 50

Since the sum of percentages (30% + 80% = 110%) exceeds 100%, there must be at least 10% who play both sports.

Explanation:

Onomatopoeia refers to words that phonetically imitate or resemble the sound they describe. "Buzz" is a perfect example because the word itself sounds like the noise bees make. Other common examples include "crash," "sizzle," "meow," "bang," and "whisper."

The other options are different literary devices:

• A simile compares two things using "like" or "as"
• Alliteration is the repetition of initial consonant sounds
• A metaphor makes a direct comparison between two unlike things without using "like" or "as"

Explanation:

Correct spelling is Etiquette.

Explanation:

Subject is singular (“teacher”), so verb should be “is.”

Explanation:

Personification  giving human traits to non-human things.
Here, the “wind” is made to “whisper,” which is a human action.

Explanation:

“Quickly” describes the manner of finishing → adverb.

Explanation:

Power P = 2 kW
= 2000 W,
time t = 60 s,
height h = 10 m,
g = 10 m/s^2
P = (m g h) / t
m = (P t) / (g h)
m = (2000 × 60) / (10 × 10) kg
 m = 120000 / 100 kg
Result (mass):
m = 1200 kg of water

Convert to volume
(ρ_water ≈ 1000 kg/m^3):
V = m / ρ = 1200 / 1000 m^3
Result (volume):
V = 1.2 m^3 = 1200 liters
The closest answer is 1000

Explanation:

Second law states heat flows naturally from hot to cold, not reverse.

Explanation:

By definition, conventional current is the flow of positive charges, though electrons actually flow opposite.

Explanation:

Formula (parallel):
1/Req = 1/R1 + 1/R2 + 1/R3
Substitute values:
1/Req = 1/2 + 1/3 + 1/6
Common denominator 6:
1/Req = 3/6 + 2/6 + 1/6
Add fractions:
1/Req = 6/6
Simplify:
1/Req = 1
Req = 1 ohm

Explanation:

Faraday’s law explains induced emf by changing magnetic flux.

Explanation:

LED emits light when forward biased.

Explanation:

Einstein used Planck’s quantum theory (photon energy E = hf) to explain photoelectric effect.

Explanation:

Explanation:

Kinetic energy depends only on speed. Since speed is constant, KE does not change.

Explanation:

Mass remains constant everywhere (10 kg). Weight varies with g.

Explanation:

Beta particles (electrons/positrons) undergo multiple Coulomb scatterings with air molecules, giving a long, tortuous zig-zag path—not straight, circular, or elliptical.

Explanation:

According to Faraday’s law, induced emf ∝ number of turns (N).

Explanation:

Equal and opposite internal forces (action–reaction) give equal and opposite momentum changes; with no external force, total linear momentum stays constant.

Explanation:

Sound waves (longer wavelength) diffract more around obstacles, while light does not.

Explanation:

Narrower slits → greater diffraction and dispersion.

Explanation:

Net force = 10 − 4 = 6 N. F = ma → a = 6/2 = 3 m/s².

Explanation:

1 N/C = 1 V/m. Both are valid units.

Explanation:

Frequency order: Radio < Visible < X-rays.

Explanation:

V = W/Q = Joule per Coulomb.

Explanation:

Half-life = 2.5 min
Time elapsed = 7.5 min
= 3 half-lives
Remaining fraction = (1/2)³
Remaining fraction= 1/8
Lost fraction = 1 − 1/8
Lost fraction= 7/8
70 µg = (7/8) × m₀
m₀ = 70 × (8/7)
m₀= 80 µg

Explanation:

Calorimeter measures heat changes.

Explanation:

Moles NaOH = 2 mol/dm³ × 0.020 dm³
= 0.040 mol
HCl needed (1:1) = 0.040 mol
Volume of HCl = 0.040 / 0.5
= 0.080 dm³ = 80 cm³
Total volume after neutralization
= 20 cm³ (base) + 80 cm³ (acid)
= 100 cm³

(Note: Acid volume required is 80 cm³; the option asks for total volume, which is 100 cm³.)

Explanation:

In molten/aqueous state, NaCl conducts electricity via ions.

Explanation:

O₂ has an O=O double bond.

CO₂ has two C=O double bonds (O=C=O).

Ethene (C₂H₄) has a C=C double bond.
(Chlorine Cl₂, hydrogen H₂, hydrogen chloride HCl are single bonds; N₂ is triple; CH₄ is all single.)

Explanation:

Potassium is soft, cut by knife, reacts vigorously with water, floats and melts.

Explanation:

HCl forms an acidic solution, not alkaline.

Explanation:

Phenol-formaldehyde (Bakelite) is a condensation polymer.

Explanation:

CaCO₃ forms as a white precipitate.

Explanation:

Zn displaces Cu: Zn + CuSO₄ → ZnSO₄ + Cu. Zinc oxidized, copper reduced.

Explanation:

Alkanes undergo substitution reactions (e.g., with halogens under UV).

Explanation:

m(N₂) = 1.4 g
M(N₂) = 28 g/mol
n = m/M = 1.4/28
= 0.05 mol
Molar volume at STP = 22.4 dm³/mol
V = n × 22.4
= 0.05 × 22.4
= 1.12 dm³

Explanation:

SiCl₄ is covalent because of small size and high electronegativity difference rule (Fajan’s rule).

Explanation:

Bond angle decreases with increased lone pairs and larger central atom. H₂S has smallest bond angle (~92°).

Explanation:

Pure esters have sharp boiling points; impurities alter this.

Explanation:

Lyman series is UV emission when electrons fall into n=1.

Explanation:

Spontaneous reactions proceed naturally, real and irreversible.

Explanation:

More shielding → weaker attraction between nucleus and electrons → lower IP.

Explanation:

Azimuthal quantum number defines orbital shape (s, p, d, f).

Explanation:

Total nodes = n − 1 = 4 − 1 = 3.

Explanation:

New shells are added → size increases.

Explanation:

Due to high reactivity, alkali metals are obtained by electrolysis of molten salts (e.g., NaCl → Na).

Explanation:

most transition elements have unpaired electrons in their d-orbitals, which makes them paramagnetic (attracted to magnetic fields).

Explanation of Wrong Options

Option b: While transition elements are generally good conductors

Option c: Transition element ions typically get their colors from d-d electron transitions (crystal field splitting), not primarily from charge transfer, though charge transfer can contribute in some cases.

Option d: The relationship between melting points and valence electrons in transition elements is not direct. Melting points depend more on factors like metallic bonding strength, crystal structure, and the number of unpaired electrons available for bonding, rather than simply the number of valence electrons.

Explanation:

Cumene process is the main industrial use of phenol.

Explanation:

The limiting reagent decides how much product can form (minimum possible).