3 The number of different planes passing through any three vertices of a parallelepiped $V$ is $m$, among which the number of planes that can bisect the volume of $V$ is $n$, then $\frac{n}{m}$ equals
A. $\frac{1}{5}$
B. $\frac{1}{4}$
C. $\frac{1}{3}$
D. $\frac{3}{10}$
3 D. Through $V$'s three vertices and bisecting $V$'s volume, the number of different planes is $3 \times 2=6$, i.e., $n=6$. The total number of different planes through $V$'s three vertices is $6+3 \times 2+8 \times 1=20$, i.e., $m=20$, hence $\frac{n}{m}=\frac{6}{20}=\frac{3}{10}$.