贫困现象体现在多种方面。（）等是导致贫困发生的主要因素。 A.性别因素 B.环境脆弱

阅读理解。

     One day, Jack and David went fishing. Jick took Tony with him on the river, when the dog saw a

bird, he wanted to run after it and tried to catch it. "All the fish are frightened and swim away," said

David, "Be quiet! Tony." Jack shouted at him. But Tony didn't listen to him. "Are we going home now,

David. Next time, I will not bring him here again." "Wait!" said David, "A fish is biting my line." "Look

out!" shouted Jack. But it was too late. The boy fell into the water, "Help! Help!" shouted David. But

Jack couldn't swim. Just then, Tony came out. He jumped into the water and pulled the boy onto the

bank and saved his life.

1. Tony is the name of ______.

A. a fish        

B. a dog          

C. a boy

2. Who didn't want to frighten the fish?

A. David        

B. Jack          

C. A and B

3. Who fell into the river and got wet?

A. David        

B. Jack            

C. Tony

4. Jack said that _______.

A. he shouldn't take Tony with him the next time

B. he shouldn't go fishing with David

C. he shouldn't go fishing

5. From the story we know _______.

A. a dog is a useful animal to us

B. we should bring a dog when we going

C. a dog can help us catch fish

We are in close contact with local authorities and it is a situation __________  we will keep a very close eye on.

A. where           B. when            C. which            D what

如图所示，水平杆上套有两个相同的质量均为m的环，两细线等长，下端系着质量为M的物体，系统静止，现在增大两环间距而系统仍静止，则杆对环的支持力F_N和细线对环的拉力F的变化情况是（　　）

A．都不变

B．都增大

C．支持力F_N增大，拉力F不变

D．支持力F_N不变，拉力F增大

什么是厂用电源的同时切换？