which directory will you find the delivered mail for the user foo?

You are running an email server configured with the default settings. In which directory will you find the delivered mail for the user foo?

A.
/var/spool/mail

B.
/home/foo/mail

C.
/var/mail/spool

D.
/var/users/mail

Explanation:
Defined in the FHS. see http://www.pathname.com/fhs/pub/fhs-2.3.html#VARMAILUSERMAILBOXFILES

In newer distributions /var/spool/mail is a link to /var/mail. This directory contains all delivered (but unread) mails for each user.