The word "malady" (Line 3, Para. 4) probably means _________.

A．All viruses are dangerous even if used properly.
B．All viruses are not so dangerous if used properly.
C．Viruses appeared later than personal computers.
D．Some viruses have been of some value to science.

A．to seldom check whether your computer is infected with viruses
B．not to open a file sent by a stranger
C．to never pass a new file through anti-virus software
D．to upgrade your program as soon as a new version comes out