How is the file format of /etc/crontab different from a normal crontab file? (Select TWO correct answers)

How is the file format of /etc/crontab different from a normal crontab file? (Select TWO correct answers)
A . The /etc/crontab file can specify a year field.
B . A normal crontab file must be installed with the crontab command.
C . A normal crontab file allows for environment variable substitution.
D . The /etc/crontab file has a user field for commands.

Answer: B,D