In many businesses, computers have largely replaced paperwork, because they are fast, flexible, and do not make mistakes. As one banker said, "Unlike humans, computers never have a bad day." And they are honest. Many banks advertise that their transactions are "untouched by human hands" and therefore safe from human temptation. Obviously, computers have no reason to steal money. But they also have no conscience, and the growing number of computer crimes shows they can be used to steal.
Computer criminals don't use guns. And even they are caught, it is hard to punish them because there are no witnesses and often no evidence. A computer cannot remember who used it: it simply does what it is told. The head teller at a New York City Bank used a computer to steal more than one and a half billion dollars in just four years. No one noticed this theft because he moved the money from one account to another. Each time a customer he had robbed questioned the balance in his account, the teller claimed a computer error, then replaced the missing money from someone else's account. This man was caught only because he was a gambler. When the police broke up an illegal gambling operation, his name was in the records.
Some employees use the computer's power to get revenge on employers they consider unfair. Recently, a large insurance company fired its computer-tape librarian for reasons that involved her personal rather than her professional life. She was given thirty days' notice. In those thirty days, she erased all the company's computerized records.
Most computer criminals have been minor employees. Now police wonder if this is "the tip of the iceberg". As one official says, "I have the feeling that there is more crime out there than we are catching. What we are seeing now is all so poorly done. I wonder what the real experts are doing—the ones who really know how a computer works."
Which feature of computers makes computer theft possible?

A．They are fast, flexible and accurate.

B．They usually function normally.

C．They have no sense of what is right or wrong.

D．They are honest and have no reason to steal money.

The author uses the case of the head teller to show_______.

A．how computer criminals so evil things

B．how hard it is to find computer criminals

C．computers lack conscience

D．computer crime can involve a big sum of money

The head teller was found guilty of stealing ________.

A．when he was caught transmitting money from one account to another

B．when the police broke up the illegal gambling operation

C．afer he was questioned on the abnormal balance of an account

D．after the police examined the illegal gambling operation documents

Why did the computer tape librarian erase all the company’s computerized records?

A．She thought it was right to revenge any injustice in professional problems.

B．She thought the employer was wrong to fire her for personal problems.

C．The company carelessly gave her enough time to do the erasing.

D．The company always interfered with its employees’ personal life.

What can we infer from the last paragraph?

A．Computer criminals are minor employees.

B．Of all crimes, computer theft is “the tip of the iceberg”.

C．Computer crimes are all poorly done.

D．There are more computer crimes committed by computer experts.