问题 单项选择题

机械波在媒质中传播过程中,当一媒质质元的振动动能的相位是π/2时,它的弹性势能的相位是:()

A.1/2π

B.π

C.2π

D.无法确定

答案

参考答案:A

阅读理解

阅读理解   

     A man is going to the house of a friend. It is quite far away so he takes some sandwiches along for

his lunch. As he goes along, he says to himself, "My friend is sure to give me a very nice meal. He is

going to give me good wine(酒) to drink. So what's the use of these dry sandwiches. "As he says this, he

throws them onto the ground.

      He goes on and comes to a river. The river has become very big because of the rain in the past few

days. He cannot cross the river. He hopes there is a boat to take him over. So he waits and waits. He

waits for a longtime. Then the sun begins to set. The man says to himself, "I cannot go to my friend's

house today. I must go home."

     Then he starts for(出发) home. Soon he feels very hungry. He wants very much to have something

to eat. But he doesn't have anything. Suddenly he sees some dry, dirty, hard sandwiches on the road. He

is very happy. He picks them up and eats them all.

      Do not throw good things away. You may need them later on.

1. It will take the man          to walk to his friend's house.

A. a few days            

B. a few hours

C. a whole night        

D. one hour or two

2. He throws the sandwiches to the ground because        .

A. he doesn't like them

B. the sandwiches are dirty

C. he thinks his friend will not like them

D. he. is sure to have a nice meal at his friend's house

3. In "the sun begins to set", "set"  here means         in Chinese.

A. 落下                        

B. 升起

C. 变暗                        

D. 照耀

4. The story tells us that we         .

A. mustn't walk a long way to visit a friend

B. mustn't throw dry sandwiches away

C. must throw things away when we don't need them

D. must always keep good things

5. He has to go back home because        .

A. it is late              

B. he hasn't got sandwiches

C. it rains hard          

D. he is hungry

单项选择题