The underlined part "in contrast" in this passage means______.

A．the computer's functions are lowered
B．the normal programs are damaged
C．all the information stored in the computer is gone
D．the computer infected by the viruses can't be used any longer

A．have been in nature for years
B．be difficult to get rid of at the present
C．be found in any computer
D．be able to get rid of in the near future