You are trying to create a new series of nested directories: /a/b/c/d/. What is the fastest way to create this nested directory set?

A) mkdir -p /a/b/c/d/
B) mkdir /a && mkdir /a/b && mkdir /a/b/c && mkdir /a/b/c/d
C) touch /a/b/c/d/
D) mkdir /a/b/c/d/