(\text{If the radius of sphere increased by 20\%, then how much percentage increase in volume?})

Volume of a sphere is proportional to the cube of its radius (V = 4/3 πr³). When radius increases by 20%, new radius = 1.2r. New volume = (1.2)³ times original = 1.728 times original. Percentage increase = (1.728 - 1) × 100 = 72.8%. Option A (33.1%) incorrectly uses linear scaling. Option B (71.8%) is close but not exact. Option D (60%) mistakenly uses 3 × 20%. Since 72.8% is not listed, E is correct.