How many thoracic vertebrae are there?

Correct Answer: B

Rationale: Twelve thoracic vertebrae (T1-T12) articulate with ribs, forming the mid-spine's curvature. Seven is cervical, five is lumbar, three is miscount. Thoracic's rib connection, per vertebral count, makes 'b' correct.

Correct Answer: A

Rationale: Intervertebral discs, fibrocartilage pads between vertebrae, absorb shock, cushioning spinal movement. Foramen houses the cord, spinous and transverse processes anchor muscles not shock absorbers. Discs' role, per spine function, makes 'a' correct.

Correct Answer: A

Rationale: All nutrient classes carbohydrates, lipids, proteins (macronutrients), vitamins, minerals (micronutrients) are essential for survival, supporting energy, structure, and regulation. Micronutrients like vitamin D can be stored, not daily required. Carbohydrates, lipids, proteins are macronutrients, not micro. Macronutrients aren't vitamins/minerals, those are micro. Essentiality of all, per nutrition, makes 'a' true.

Correct Answer: C

Rationale: PET (Positron Emission Tomography) tracks metabolic activity, like nutrient uptake in cancer cells, using radioactive tracers (e.g., glucose), ideal for rapid proliferation studies. CT shows structure, MRI details tissues, ultrasonography uses sound none measure metabolism directly. PET's functional focus, per imaging, makes 'c' best.

Correct Answer: C

Rationale: Lactic acid accumulates in fatigued skeletal muscles when oxygen supply lags demand, shifting metabolism to anaerobic glycolysis. Normally, pyruvate from glucose enters mitochondria for aerobic respiration, yielding ATP efficiently. During intense exercise, oxygen depletion forces pyruvate conversion to lactate via lactate dehydrogenase, releasing NAD+ to sustain glycolysis and ATP production, though less efficiently. This occurs in skeletal muscle, not exclusively cardiac, which relies more on aerobic pathways. Rested muscles with oxygen use aerobic metabolism, avoiding lactate buildup. Fatigued muscles with oxygen continue aerobic respiration, not glycolysis. Rested muscles lacking oxygen are hypothetical, as rest implies oxygen availability. Exercise physiology confirms lactate rises in anaerobic conditions blood levels can jump from 1 to 20 mmol/L in fatigue causing acidity and signaling exhaustion. This adaptive mechanism delays fatigue, distinguishing it from aerobic states or unrelated muscle types, a key insight into metabolic flexibility.