单选题 The computer network is a creation of the electronic age. In a computer system, a hacker is worse than a thief entering your house. He could go through anyone's electronic mail or add to, change, distort or delete anything in the information stored in the computer's memory. He could even take control of the entire system by inputting his own instructions in the software. He could shut the computer down whenever he wished, and no one could stop him. Then he could program the computer to erase any sign of his ever having been there.
Hacking, our electronic-age term for computer break-in, is more and more in the news: A dissatisfied former insurance-company employee wipes out information from payroll files. A student sends out a "virus", a secret and destructive command, over a national network. The virus copies itself at lighting speed, jamming the entire network--thousands of commercial and government computer systems. Now exists the possibility of terrorism by computer. Destroying a system responsible for air-traffic control at a busy airport or the telephones of a major city is a relatively easy way to spread alarm.
Yet neither business nor government has done enough to strengthen its defenses against attack. For one thing, such defenses are expensive; for another, they may interrupt communication--the main reason for using computers in the first place.

单选题 Why does the writer mention "a thief" in the first paragraph? ______
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.

单选题 Find the same meaning as "erase" in the last sentence of the first paragraph.
A. Add. B. Change. C. Remove. D. Store.

单选题 According to the passage, all the damage listed below could be done by a hacker EXCEPT ______.
A. entering into computers illegally
B. creating many electronic-age terms
C. removing computer systems
D. going through computer systems

单选题 By saying "Now exists the possibility of terrorism by computer", the writer means that ______.
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

单选题 The main reason why business or government has not taken tough measures to stop hacking is that ______.
A. they will cost too much money B. communication may be interrupted
C. hacking has not caused much damage D. tough measures are illegal