On October 12,1989，some British scientists were working at the computers to look for the information they needed.Suddenly they saw a lot of very bright points crossing the computer screens.At the same time the computers were working much slower.To find out what was happening they stopped their work to check some parts of the computers.To their horror，they found out that most of their stored information was got rid of by computer viruses(病毒)！Clearly all these computers had been infected by computer viruses.
It is said that the computer viruses were made by a group of young men fond of playing tricks.They all had excellent education.They created the viruses just to show their intelligence. These kinds of computer viruses are named Jerusalem Viruses.These viruses can stay in computers for a long time.When the time comes they will attack(袭击)the computers by lowering the functions，damaging their normal programs or even getting rid of all the information.
We now come to know that Jerusalem Viruses often attack computers on Friday and that they are spreading(传播)to a lot of computers.Among the countries that were attacked by computer viruses last year are Britain，Australia，Switzerland and the U．S.But till now，how to get rid of the terrible viruses remains a problem.
When the viruses attack the computers，the computers will work________.

A．normally

B．slowly

C．faster

D．well

The group of young men created the viruses to________.

A．damage the computers

B．test their ability

C．tell people that they were intelligent

D．play a trick on users of the computers

According to the passage，computer viruses seem to ________.

A．have been in nature for years

B．stay in any computers

C．be difficult to get rid of at present

D．be able to be got rid of in the near future

According to the passage，which of the following is TRUE?

A．Last year six countries found their computers were infected by viruses.

B．The viruses will come to a new computer after staying in the old one for some time.

C．Scientists are trying to find a way to get rid of the viruses.

D．The Jerusalem Viruses are dangerous to human health.