看图，选择正确的答案。

1. Are there any mountains in the picture? 

A. Yes, there aren't.

B. No, there aren't.

C. Yes, there are.

2. Is there a river in the picture?

A. Yes, there is.

B. No, there isn't.

C. Yes, it is.

3. How many ducks can you see? 

A. I can see two.

B. I can see three.

C. I can see four.

4. How many people are there?

A. There are two.

B. There are three.

C. There are four.

5. How many bridges are there?

A. There are two.

B. There is only one.

C. I can see only one.

6. Is there a city m the picture? 

A. Yes, there is a city in the picture.

B. No, there isn't.

C. No, it isn't a city.

特异度是指（）。

A．实际有病按诊断标准判为无病的百分比

B．实际有病按诊断标准判为有病的百分比

C.实际无病按诊断标准被正确判为无病的百分比

D．实际无病按诊断标准判为有病的百分比

E.阳性结果中真正无病的人所占百分比