Read the Assertion and Reason below and choose the correct option. — Solid State Chemistry Question

💡 Solution & Explanation

The nearest neighbour distance in BCC is $\frac{\sqrt{3}a}{2} \approx 0.866a$, while in FCC it is $\frac{a}{\sqrt{2}} \approx 0.707a$. Since $0.866a > 0.707a$, the assertion is true. This closer packing in FCC reflects its higher overall packing efficiency (74%) compared to BCC (68%), making the reason the correct explanation. Therefore, correct answer is A.