阅读理解。

       Tom and Mike are good friends. They are kind to children. They want to find summer jobs(暑期工作). The Children’s Palace( 少年宫) needs some P.E. , music and computer teachers. They are very

happy to hear(听说) this.

       Tom can play basketball and volleyball, and he can swim, too. Mike can play the violin, the piano and

the guitar. Tom and Mike like computers very much. Can they join（加入）the Children’s Palace?

1. Tom and Mike ________________.

A. brothers      

B. teachers          

C. sisters      

D. good friends

2. The Children’s Palace needs some              .

A. dogs        

B. cats            

C. teachers      

D. students

3. Tom can play ________________________.

A. balls

B. computer games  

C. music

D. the violin

4. Mike can play ____________________.

A. the piano

B. piano   

C. guitar

D. football

5. What do Tom and Mike both(都) like?

A. Football.

B. Computers.

C. Swimming.

D. Sports.

实验室用以下两种方法制取氧气．方法一：分解氯酸钾；方法二：分解过氧化氢溶液．请回答下列问题．

（1）方法一或方法二都要用到另外一种相同的物质，该物质的化学式是______，在反应中的作用是______．

（2）写出反应的化学方程式．

方法一：______；  方法二：______．

（3）比较两种方法，方法二的主要优点是______．

（4）现有500g 质量分数为3.4%的过氧化氢溶液．该溶液中含过氧化氢______g，最多可以制得氧气______g．