How could a user arrange for a command to be run daily at a certain time on a Linux system, using the cron service?

A.
Create a file to specify the schedule, and use crontab to install the file.

B.
Use a text editor to create a file in /var/cron that specifies the schedule.

C.
Edit /etc/periodic/cron.daily

D.
Specify the schedule using entries in a file at /etc/cron.conf