Atomic layers from thickness divided by diameter Steps:

• Convert sheet thickness to picometers: 0.25 μm = 0.25 × 10⁶ pm = 250,000 pm.
• Calculate atomic diameter: 2 × radius = 2 × 174 pm = 348 pm.
• Divide thickness by diameter: 250,000 pm ÷ 348 pm ≈ 718.
• Round to nearest option: approximately 700 layers.

Why D is correct:

• Direct division of thickness by atomic diameter gives ~718, closest to 700 per unit conversion and basic atomic spacing approximation.

Why the others are wrong:

• A. 4 results from treating thickness as 0.25 pm instead of 250,000 pm.
• B. 7 arises from dividing 2.5 (from 0.25 × 10) by ~0.35, ignoring full unit conversion.
• C. 400 comes from erroneously using ~625 pm diameter or halving the thickness value.

Final answer: D