题目内容：

    It began as a game: High school and college students studying computer technology figured out they could use personal computers to break into telephone company computers and make free, long-distance telephone calls. These young computer talents soon gained the name "hackers".

Police arrested a few hackers, but many went on to even more complex hacking. One of them was arrested for making illegal telephone calls and later he used a phone to change a police officer's credit records to get back at the officer for arresting him. He also used a computer to change his college records to give himself better grades.

As hackers gained experience, they began invading computers at banks, airlines and other businesses. In one case a hacker instructed an airline' s computer to give him free airplane tickets.

The U.S. government is worried that hackers may break into its networks of defense computers. The government's secrets are easily attacked because thousands of government computers are connected by telephone lines that hackers can get into.

In November 1988, a college student entered a U.S. Defense Department computer network called Arpanet. The hacker injected a computer program that made copies of itself throughout Arpanet. Some hackers use viruses to destroy all the data in a computer. But in this case, government officials shut down the network before the program reached every computer in the system. Shutting down the system angered many researchers who were using the computers. The hacker turned himself in to the police and he was charged with a crime.

The incident put the spotlight on computer hacking in the United States. Many companies have hired experts to protect their computers from hackers, and many computer experts now advise companies on how to protect their computers.

The U.S. government believes foreign governments have hired hackers to try to break into top-secret defense computers.

Experts disagree over whether a computer network can ever be safe from hacking. But in the future, some of the most outstanding minds in the U.S. will be working to frustrate the attempts of computer hackers.

1.What did the first hackers do?

A. They broke into government computers. B. They destroyed airplane ticket systems.

C. They played computer games. D. They made free phone calls.

2.Why can U.S. government computers be easily hacked into?

A. They have no defense systems. B. They are connected by telephone lines.

C. They are partly accessible to the public. D. They lack complex processing programs.

3.What happened to the government computers in November 1988?

A. They lost all of the important data.

B. They were shut down by researchers.

C. They were invaded by a college student.

D. They got totally ruined by a computer program.

4.What did companies decide to do to protect their computer systems?

A. Employ computer talents. B. Build secret defense systems.

C. Ask the government for help. D. Collect and analyze the data of hackers.