Lane Received a Phone Call from a Client

Multiple Choice

Lane received a phone call from a client. The client claimed that a file he was working on the day before had disappeared from his computer along with several other files. Lane went to the client's desk to see if she could rebuild the files from the backup done the night before. Lane found and rebuilt the files from the backed-up data. When Lane called the next morning to see if everything was working, the client said that two of his files were gone again. He also noticed new files in a folder. When Lane arrived, she checked to see how much free space the computer had available and found that it had 250GB less than the day before.  
What is the issue with the client's computer?

A) Spam
B) Corrupt hard drive
C) Bad hard drive driver
D) Computer virus