An intruder attempted malicious activity and exchanged emails with a user and received corporate information, including email distribution lists. The intruder asked the user to engage with a link in an email. When the link launched, it infected machines and the intruder was able to access the corporate network.
Which testing method did the intruder use?

A.	social engineering
B.	eavesdropping
C.	piggybacking
D.	tailgating