Which of the following is the purpose of the ??in Smith’s password field?

The following is an extract of a password file:

Smith:*:1133:334:John Smith:/usr/people/jsmith:/bin/tcsh

Which of the following is the purpose of the ??in Smith’s password field?

A.
It indicates that Smith is a superuser.

B.
It deactivates Smith’s account.

C.
It forces Smith to change his password at his next login.

D.
It indicates that Smith’s home directory is shared by other members of his group.