What pigment is responsible for skin color?

Correct Answer: B

Rationale: Melanin, produced by melanocytes in the stratum basale, determines skin color, ranging from light to dark, and protects against UV by absorbing it. Hemoglobin colors blood, visible through skin but not primary. Carotene adds yellowish tones, minorly. Keratin is a structural protein, not a pigment. Melanin's dominant role in pigmentation and photoprotection, per dermatology, makes 'b' correct.

Correct Answer: D

Rationale: The vertebral column protects the spinal cord (not heart, a), supports the head , and allows movement/flexibility via joints e.g., cervical flexion. Heart protection is rib cage/sternum. All functions apply, per spinal anatomy, making 'd' correct.

Correct Answer: A

Rationale: Five lumbar vertebrae (L1-L5) form the lower back, supporting weight and flexibility. Seven is cervical, twelve is thoracic, three is miscount. Lumbar's count, per spinal anatomy, makes 'a' correct.

Correct Answer: C

Rationale: Synovial joints (e.g., shoulder) allow the most movement flexion, rotation via fluid-filled capsules. Fibrous are immovable (sutures), cartilaginous slightly movable (vertebrae). Synovial's range, per joint types, makes 'c' correct.

Correct Answer: C

Rationale: Humans need oxygen most urgently, surviving only minutes without it, as it fuels cellular respiration (ATP production) via lungs. Food sustains days, water hours to days, nitrogen isn't directly needed (it's in air, not a pressing requirement). Oxygen's immediate necessity, per survival physiology, makes 'c' correct.