考核一种疫苗效果时进行双盲设计是指()
A.设计者和观察者都不知道哪些受试者接受疫苗，哪些受试者接受安慰剂
B.受试者和观察者都不知道哪些受试者接受疫苗，哪些受试者接受安慰剂
C.受试者和设计者都不知道哪些受试者接受疫苗，哪些受试者接受安慰剂
D.接受疫苗者和接受安慰剂者都不知道自己是试验对象
E.接受疫苗者和接受安慰剂者都不知道试验的目的
参考答案：B
| 根据下面的对话内容，从对话前的选项中选出能填入空白处的最佳选项，并将其选项标号填入文后 的答栏内。选项中有一项为多余选项。
| |
| A: Hi, Maggie! Did you go to the concert last night? B: Yes. My father had two tickets and _______(1) A: _______(2) B: Fantastic. Many famous singers and movie stars gave performances at the concert. _______(3) A: What does it mean? B: _______(4) You know many children in poor areas of China don't have chances to go to school. A: _______(5) B: I think people all over China should help them. A: That's right! |