A、 The American population increased by 40 percent.
B、 So many school children died of polio in the nation.
C、 A polio plague swept the nation.
D、 A polio vaccine was developed.

【正确答案】 D

【答案解析】解析：录音讲到40年前美国的孩子面临着患脊髓灰质炎的危险，但是一种vaccine的发现帮助了school children 40 years ago抵御了这种病的袭击。

A、 A vaccine for polio.
B、 A rare form of cancer.
C、 A disease similar to AIDS.
D、 A virus from monkeys.

【正确答案】 D

【答案解析】解析：录音讲到这种疫苗受到了a virus from monkeys的污染，这种病菌叫做SV 40。

A、 They were at risk of getting cancer.
B、 they became victims of poliomyelitis.
C、 They were involved in a medical investigation.
D、 They were injected with tainted vaccines.

【正确答案】 D

【答案解析】解析：1955年到1963年之间大批的疫苗受到了SV 40这种细菌的污染，而young children in37 states意外地接受了注射。

A、 30 percent.
B、 40 percent.
C、 50 percent.
D、 60 percent.

【正确答案】 A

【答案解析】解析：录音讲到美国过去的20多年间brain tumors增长了30 percent。

A、 All the injections given 40 years ago were contaminated.
B、 The contaminated vaccines may cause cancer in humans.
C、 Vaccines are responsible for brain tumors.
D、 Brain tumors had increased by 40% .

【正确答案】 C

【答案解析】解析：专家指出SV 40是脑瘤患者增长的一个possible reason，这一增长可能与tainted(受污染的)vaccine有关。