A small company would like help in identifying an apparent system performance problem on its internal mail server， especially to determine peak hour usage. What would be the first step in identifying the problem？（）

A. cd /var/spool/cron/crontabs，uncomment the lines in the adm file， in order to start gathering statistics.
B. cd /var/spool/cron/crontabs； uncomment the lines in the sys file， in order to start gathering statistics.
C. cd /usr/lib/cron/； vi the adm file； startsrc -s sadc
D. cd /usr/lib/cron/； vi the sys file； startsrc -s sadc