Why should a regular user edit his personal crontab by using the command crontab instead of just editing his crontab file manually?

Why should a regular user edit his personal crontab by using the command crontab instead of just
editing his crontab file manually?

A.
Because user specific crontab entries are stored in a common database and must be extracted
before editing.

B.
Because crontab starts the cron daemon in case it is not running due to no other crontab
entries existing.

C.
Because user specific crontab entries are stored in a special directory which is maintained by
the cron daemon and not writable for regular users.

D.
Because crontab collects information about all users crontabs and recommends similar
commands used by other users of the system.

Explanation: