描述磁场中各点磁场强弱和方向的物理量，称为( )或磁通密度，用符号B表示，单位名称

阅读理解。

     Mr. Green is a teacher. His only son, Bill, is a student. He is twelve. The child likes to fly kites and play

some other games. One Monday afternoon, Bill flies kites with his friends after school. But Bill's kite is in

the tree. and he can not get it. Bill and his friends do not know what to do. They worry very much and Bill

goes to his father for help. His father wants to get the kite down from the tree, but he can't. So Bill asks

him to make a new one for him.The man makes a new kite. When the boy gets the new kite, he is very

glad. He thanks his father for the kite and goes out to play with his friends.

1. How many children are there in Mr. Green's family?

A. Two

B. One

C. Three

D. We don't know

2. Bill likes to _____.

A. play other games

B. fly kites only

C. make kites

D. play games

3. One day _____.

A. Bill finds a kite in a tree

B. Bill's kite is broken and it is in the tree

C. Bill's friends mend his kite

D. Bill makes a kite for his friends

4. Bill is glad because _____.

A. he helps his friends get the kite down from the tree

B. his friends do not know what to do

C. his father helps him get him get the kite down

D. Mr. Green makes a new kite for him

5. From the text we can see _____.

A. Bill can not get the kite down but his friends don't' worry very much

B. Bill's father can not get the kite down, so he makes a new kite

C. Mr. Green can not get the kite down and wants to make a new one for Bill

D. Bill's friends break the kite and help Bill make a new one

---Please remember me ___ your family. ----I certainly will

A．with

B．for

C．about

D．to

人力激励是指什么？

减少底片上水迹的方法是温胶片快速干燥。

防止燃气爆炸的首要措施是防止燃气的（），使其不能达到爆炸极限。

A、泄漏

B、积聚

C、泄漏和积聚

D、着火源