The best title of this passage is ______.

A．To show that a hacker is more dangerous than a thief.
B．To tell people that thieves like to steal computers nowadays.
C．To demand that a computer network should be set up against thieves.
D．To look into the case where hackers and thieves are the same people.

A．some employees may erase information from payroll files
B．students who send out a "virus" may do damages to thousands of computers
C．some people may spread fear in public by destroying computer systems
D．some terrorists are trying to contact each other using electronic mails