While browsing the Internet, an administrator notices their browser behaves erratically, appears to download something, and then crashes. Upon restarting the PC, the administrator notices performance is extremely slow and there are hundreds of outbound connections to various websites. Which of the following BEST describes what has occurred?

A.
The PC has become part of a botnet.

B.
The PC has become infected with spyware.

C.
The PC has become a spam host.

D.
The PC has become infected with adware.