A.fff\(\frac{2}{5}d\)/fff
B.fff\(\frac{5}{2}d\)/fff
C.fff\(\frac{4}{25}d^{2}\)/fff
D.fff\(\frac{2}{5}d^{2}\)/fff
E.fff\(\frac{2}{3}d^{2}\)/fff
我的答案：
