?He brings up his Task Manager and sees the following programs running (see screenshot):What has William just installed?

William has received a Tetris game from someone in his computer programming class through email.William does not really know the person who sent the game very well, but decides to install the game anyway because he really likes Tetris.
After William installs the game, he plays it for a couple of hours.The next day, William plays the Tetris game again and notices that his machine has begun to slow down.?He brings up his Task Manager and sees the following programs running (see screenshot):
What has William just installed?

A.
Zombie Zapper (ZoZ)

B.
Root Digger (RD)

C.
Bot IRC Tunnel (BIT)

D.
Remote Access Trojan (RAT)

Explanation:
RATs are malicious programs that run invisibly on host PCs and permit an intruder remote access and control. On a basic level, many RATs mimic the functionality of legitimate remote control programs such as Symantec’s pcAnywhere but are designed specifically for stealth installation and operation. Intruders usually hide these Trojan horses in games and other small programs that unsuspecting users then execute on their PCs. Typically, exploited users either download and execute the malicious programs or are tricked into clicking rogue email attachments.