What must be done to direct example.org email towards fred?

The mailserver is currently called fred, while the primary MX record points to mailhost.example.org. What must be done to direct example.org email towards fred?

A.
Add an A record for mailhost to fred’s IP address.

B.
Add a CNAME record from mailhost to fred

C.
Add another MX record pointing to fred’s IP address.

D.
Add a PTR record from mailhost to fred.