Anti-spam software can prevent unwanted mail by either filte

Anti-spam software can prevent unwanted mail by either filtering incoming messages with the aid of rule-based filters or asking users to blacklist the addresses sending them junk mail.

A. asking users to blacklist the addresses sending them
B. asking users to blacklist the addresses, sending them
C. by asking users to blacklist the addresses from which they are sent
D. ask users to blacklist the addresses sending
E. by asking users to blacklist the addresses that send

OA A

Source: Economist Gmat