The MOST common cause of hypokalemia in children is

Correct Answer: C

Rationale: Gastroenteritis is the most common cause of hypokalemia in children due to potassium loss via diarrhea.

Correct Answer: D

Rationale: Hypotension can impair ventilation, causing CO₂ retention and respiratory acidosis.

Correct Answer: B

Rationale: Gowers sign, a classic indicator of proximal muscle weakness seen in Duchenne muscular dystrophy, typically becomes fully evident by age 5 as the child struggles to rise from the floor.

Correct Answer: D

Rationale: Hypoparathyroidism does not typically cause myopathy; the others can, via mechanisms like steroid-induced muscle breakdown or thyroid hormone effects on muscle metabolism.

Correct Answer: C

Rationale: Lower limb weakness is not a core feature of MFS, which focuses on ophthalmoplegia, ataxia, and areflexia.