简述低压熔断器的作用及分类。

能与IL-4协同刺激朗格汉斯细胞分化为树突状细胞的细胞因子是（）

A.IL-4

B.IL-7

C.IL-11

D.EPO

E.GM-CSF

一家珠宝店的珠宝被盗，经查可以肯定是甲、乙、丙、丁中的某一个人所为。审讯中，甲说：“我不是罪犯。”乙说；“丁是罪犯。”丙说：“乙是罪犯。”丁说：“我不是罪犯。”经调查证实四人中只有一个人说的是真话。 根据已知条件，下列哪个判断为真( )

A．甲说的是假话，甲是罪犯

B．乙说的是真话，丁是罪犯

C．丙说的是真话，乙是罪犯

D．丁说的是假话，丁是罪犯

I receive many letters from children and can’t answer them all – there wouldn’t be enough time in a day. I’ll try to answer some of the questions that are commonly asked.

Where did I get the idea for Stuart Little and for Charlotte’s Web? Well, many years ago, I went to bed one night in a railway sleeping car, and during the night I dreamed about a tiny boy who acted rather like a mouse. That’s how the story of Stuart Little got started.

As for Charlotte’s Web, I like animals and my farm is very pleasant place to be – at all hours. One day, when I was on my way to feed the pig, I began feeling sorry for the pig because, like most pigs, he was going to die. This made me sad. So I started thinking of ways to save his life. Three years after I started writing it, it was published. (I am not a fast worker, as you can see.)

Sometimes I’m asked when I started to write, and what made me want to write. I started early – as soon as I could spell. Children often find pleasure through trying to set their thoughts down on paper, either in words or in pictures. I was not good at drawing, so I used words instead. As I grew older, I found that writing could be a way of earning a living.

Well, here is the answer to the last question. No, they are imaginary (虚构的) tales. In real life, a family doesn’t have a child who looks like a mouse and a spider doesn’t write words in her web. Although my stories are imaginary, I like to think that there is some truth in them, too – truth about the way people and animals feel, think and act.

小题1:E.B. White wrote this passage to ______.

A. introduce his new books

B. introduce two funny stories

C. explain why he enjoys writing

D. answer some readers’ questions

小题2:We can know from the passage that E.B. White is a writer who ______.

A. writes very fast

B. works on a friends’ farm

C. mainly writes stories for adults

D. writes imaginary tales for children

小题3:What inspired E.B. White to write Charlotte’s Web?

A. That he wanted children to love animals.

B. That he was deeply impressed by a clever pig.

C. That he wanted to use his own way to save a pig.

D. That he wanted to save the animals on a farm.

小题4: E.B. White started to write because he wanted to ______.

A. improve his spelling

B. express his thoughts

C. show his sadness

D. make a good living

小题5:What is probably the last question?

A．Are your stories true?

B．What is the truth in your stories?

C．Will you write more imaginary tales?

D．Do you know a child looking like a mouse?

下列试剂的贮存方法中正确的是[ ]

①浓硝酸存放在棕色试剂瓶中 ②少量白磷存放在水中 ③液溴保存在水中

④少量金属钠贮存在煤油中 ⑤氢氟酸保存在玻璃瓶中 ⑥烧碱溶液盛放在带玻璃塞的玻璃瓶中

A．全对

B．只有①②③

C．只有①②③④

D．只有⑤⑥

液压泵反馈故障生成条件（）

A.PLC收到建压要求，持续4秒钟没有得到液压站电机启动的反馈信号时，风机立即报此故障

B.当液压站系统压力建压达到160bar后，持续4秒钟液压站电机反馈信号没有消失，立即报此故障

C.PLC收到建压要求，仍没有得到液压站电机启动的反馈信号时，风机立即报此故障

D.当液压站系统压力建压达到160bar后，液压站电机反馈信号仍没有消失，立即报此故障