烃类油捕收剂作用及机理。

事故所处的阶段一般分为（）。

A．事故潜伏期

B．慢性危险期

C．事故爆发期

D．事故维持期

E．事故消解期

下列数据3，2，3，4，5，2，2的中位数是【   】

A．5

B．4

C．3

D．2

气态中性原子失去一个电子转化为气态正离子所需要的最低能量叫做第一电离能（I₁），气态正离子继续失去电子所需最低能量依次称为第二电离能（I₂）、第三电离能（I₃）……下表是第三周期部分元素的电离能［单位：eV（电子伏特）］数据.

元素	I1/eV	I2/eV	I3/eV
甲	5.7	47.4	71.8
乙	7.7	15.1	80.3
丙	13.0	23.9	40.0
丁	15.7	27.6	40.7

下列说法正确的是（   ）

A．甲的金属性比乙强         B．乙的化合价为＋1价  

C．丙一定为金属元素         D．丁一定是金属元素

阅读理解。

     A young woman carrying a three-year-old child got on a bus. The conductor hurried to give her a warm

welcome and then kindly asked the other passengers to make more room for the woman and her child. On

seeing this, people began to talk. "You know this conductor used to be very rude. Now suddenly he has

changed his bad behavior," said a middle-aged man. 

     "Yes, he should be praised and we must write a letter to the company," said a second passenger. "That's

right," another lady said, "I wish a newspaper reporter were here so that more people could learn from this

conductor."

     Just then a gentleman who looked like a teacher turned to the conductor and said, "Excuse me, but can

I know your name, please? Your excellent service must be praised..." 

     Before he could open his mouth, the three-year-old child sitting on the young woman's lap interrupted,

"I know his name. I call him Dad."

1. One passenger suggested writing a letter to the company to _____.

A. make a demand for more buses

B. thank the conductor for his good service

C. criticize the conductor for his rude behavior

D. invite a newspaper reporter to write about the conductor

2. What was the gentleman?

A. A teacher.

B. A newspaper reporter.

C. Not known from the story.

D. The conductor's friend from his company.

3. The word "him" in the last paragraph refers to _____.

A. the gentleman

B. the conductor

C. the middle-aged man

D. the three-year-old child

4. It is clear from the story that the conductor _____.

A. has changed his attitude towards his work

B. has now been kind and polite to all passengers

C. has not changed his rude behavior to passengers

D. has now been kind and polite to women with children

阀门的公称压力通常用（）表示。

A.℃

B.P

C.Pg

D.mm