21. A. familiar　　　　　　　 　　　 B. wrong　　　　　　　　　　　 C. connected　　　　　　　　 D. bored

55. The underlined word "This" in the last paragraph means “　　　　 ”.

　　　 A. Leah died after a single Ecstasy tablet in 1995.

　　　 B. people have long known that repeated use of the drug damages brain cells

　　　 C. occasional use of the drug can have long-lasting effects on one’s brain systems

　　　 D. taking drug has the same symptoms as smoking

54. Why are squirrel monkeys and baboons involved in the experiments?

　　　 A. Because their brain is similar to human being’s

　　　 B. Because these animals usually take drugs.

　　　 C. Because these animals will soon get well after the experiment.

　　　 D. Because there is a model in the animals’ brains.

53. We know from the passage that low doses of Ecstasy 　　　　.

　　　 A. won’t cause serious brain damage

　　　 B. can permanently destroy one’s brain cells

　　　 C. can’t show any effect in an experiment

　　　 D. may bring on Parkinson’s at once

52. According to the passage, Parkinson’s is 　　　　.

　　　 A. the name of a scientist 　　　　　　　　　　　　 B. a kind of brain cell

　　　 C. be name of an animal　 　　　　　　　　　　　　 D. a kind of disease

51. The article is intended to　　　 .

　　　 A. explain the effects of the drug Ecstasy on many different brain systems

　　　 B. warn youngsters of the risk of taking the drug Ecstasy

　　　 C. convince people of the abuse of the drug Ecstasy

　　　 D. tell us the links between the drug Ecstasy and Parkinson's disease

50. In some countries, the governments control the installment plan to 　　　　.

　　　 A. increase employment

　　　 B. avoid depressions

　　　 C. ensure that businesses make good profits

　　　 D. ensure that people can pay for what they buy

C

A single night of taking the drug Ecstasy(摇头丸) can cause serious brain damage and speed up the start of Parkinson's disease, scientists say. Just two to three Ecstasy tablets -- a quantity that thousands of clubbers take during parties -- can permanently destroy brain cells that affect movement and reasoning, according to American research that links the drug to Parkinson's for the first time.

A study by a team at Johns Hopkins University in Baltimore, Maryland, involving squirrel monkeys and baboons(狒狒) found that both species suffered permanent damage to key cells called dopamine neurons, which are lost in Parkinson's, after receiving three low doses of Ecstasy at three-hour periods.

The study is particularly significant because baboons are one of the best animal models for the human brain. George Ricaurte, who led the research, said that widespread abuse of the drug may already be claiming victims of such neurological(神经性的) damage. “The most troubling result is that young adults using Ecstasy may be increasing their risk for developing Parkinsonism as they get older.”

Alan Leshner, a former director of the US National Institute on Drug Abuse, said: “This study emphasizes the multi-aspect damage that Ecstasy can do to users. We've long known that repeated use damages brain cells. This study shows that even very occasional use can have long-lasting effects on many different brain systems. It sends an important message to young people: don't experiment with your own brain.”

Janet Betts, the Essex mother whose daughter Leah died after a single Ecstasy tablet in 1995, said: “This comes as no surprise. People can't see the effects at first, and they’re in permanent denial(否认), saying it's not going to happen to them. But we'll see the symptoms later, just as we have with smoking.”

49. The advantage of installment buying might include all the following EXCEPT that 　　　　.

　　　 A. purchasing power is strengthened.

　　　 B. employment might be increased

　　　 C. people develop a good habit of saving money

　　　 D. young couples are able to furnish their homes

48. What will happen to a buyer if he fails to make the full payment for an item bought on installments?

　　　 A. He might lose his job.

　　　 B. He will stop owning the item he has bought.

　　　 C. He will have to sell what he has bought.

　　　 D. He will go into debt.

47. Goods bought on installments are more expensive than goods bought by cash because 　　　.

　　　 A. the buyer has to pay extra money as interest

　　　 B. the delivery of the goods charges extra money

　　　 C. the buyer has to pay a down payment

　　　 D. the service offered by installment plan charged extra money