问题 单项选择题 A3型题

为考核口服痢疾弧菌疫苗预防细菌性痢疾的效果,将1000名研究对象随机分成疫苗组和对照组,两组分别500人。以血清抗体的阳转和细菌性痢疾发病率的下降为结局变量指标,随访观察2年时间。研究结果表明,疫苗组的痢疾杆菌抗体阳转者450人,对照组的抗体阳转者50人;疫苗组发生细菌性痢疾病人15人,对照组发生细菌性痢疾病人60人。

该研究中疫苗对细菌性痢疾的保护率是()

A.89%

B.0.3%

C.1.2%

D.90%

E.75%

答案

参考答案:E

阅读理解

阅读短文,回答问题。

     Sam likes eating fish very much. He often buys fish in the shop and takes them home. One day his

wife sees the fish and thinks, "Good! Now, I can ask my friends to have lunch and we can eat the fish.

They like fish very much. "

     When Sam comes home from work in the evening, the fish is not there and his wife says, "Oh, your

cat eats it. "And then she gives him some bread for his supper. Sam is angry (生气). He takes the cat and

his wife to a shop near his house and weighs(称)the cat. Then he turns to his wife and says, "My fish

weighs one kilo. The cat weighs one kilo, too. My cat is here, you see, then, where is my fish? "

1. What does Sam like eating very much?

                                                                         

2. Who eat the fish that day?

                                                                         

3. How much does the fish weigh?

                                                                         

4. What does Sam's wife give him for supper?

                                                                         

5. Can you guess if (是否)Sam knows where the fish is?

                                                                          

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