Which of these commands will work? If a command doesn't work, why?

a$)>$ mkdir a$/$b$/$c

b$)>$ mkdir a a$/$b a$/$b$/$c

c$)>$ rmdir a$/$b$/$c

Note: You must place some files under the c directory before you try this command.

d$)>$ rmdir a a$/$b

Note: Make sure the $b$ directory is empty before you try this command.