Which cells are responsible for bone resorption?

Correct Answer: C

Rationale: Osteoclasts resorb bone, breaking down matrix via enzymes/acids to release calcium, balancing remodeling. Osteoblasts form bone, osteocytes maintain it, and chondrocytes produce cartilage, not bone resorbers. Osteoclasts' destructive role, per bone physiology, makes 'c' 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.

Correct Answer: D

Rationale: Röntgen won the 1901 Nobel for discovering X-rays, electromagnetic waves revealing internal structures (e.g., bones), revolutionizing medicine. Nuclear physics was later, radiopharmaceuticals involve isotopes, radiation-cancer link wasn't his focus. X-rays' impact, per history, makes 'd' correct.