腐蚀介质的处理包括（）。A、锅炉给水的除氧 B、调节介质的PH值 C、改变介质的湿度

阅读理解。选择正确答案。

      John is a bookseller. He doesn't like paying for anything. One day he leaves a box of books on his foot.

" Go to the doctor." says his wife. " No," he says, " I'll wait till the doctor comes into the shop next time.

Then I'll ask him about my foot. If I go to see him, I'll have to pay for him."

      The next day the doctor comes into the shop and buys some books. When John is getting them ready,

he tells the doctor about his foot. The doctor looks at it, " Yes," says the doctor, " You must put the foot in

hot water every night." " Thank you," says the bookseller, " And now sir, here are your books." " How much? "

says the doctor, " Two pounds," answers John. " Good," says the doctor, " I shall not have to pay you

anything." " Why? " asks John in surprise, " I tell you about your foot. I want two pounds for that. Goodbye."

1. John is a _____________.

A. worker

B. doctor

C. book maker

D. bookseller

2. The bookseller's wife tells him to _____________.

A. wait for the doctor coming

B. go to the doctor

C. be careful when he does things

D. ask the doctor to come

3. The doctor comes into the shop to _____________.

A. buy some books

B. look at John's foot

C. pay John some money

D. look at medicine books

4. When does the bookseller tell the doctor about his foot?

A. When the doctor comes into the shop.

B. When he is getting the books ready.

C. After he hands the books to the doctor.

D. After the doctor has books in his hand.

实验室常用制取氧气的方法有：

a．加热氯酸钾和二氧化锰粉末；

b．加热高锰酸钾固体；

c．用二氧化锰粉末作催化剂使过氧化氢（H₂O₂）溶液分解产生氧气．其实验装置如图所示．

（1）写出上图中指定仪器的名称：

①______；③______．

（2）利用装置A制氧气，棉花团的作用是______；利用装置B制氧气时，长颈漏斗的下端要插入液面以下，其目的是______．

（3）用文字表达式表示高锰酸钾制取氧气的化学反应反应式______．

（4）实验室用高锰酸钾制取氧气并用排水法收集氧气，实验结束后，收集到的氧气不纯其原因是：______．

二叉树与树都可以用二叉链表作为存储结构，二者的关系是( )。

A．一棵树可以惟一对应一棵二叉树

B．一棵二叉树惟一对应一棵树

C．一棵与树对应的二叉树左子树为空

D．二者没有确定的对应关系

下列有机物水解断键处不正确的是（   ）

上二黄丸功效与作用