机泵单向阀的作用是防止（）造成损坏机泵事故。

请根据上下文内容，将文中画线部分译成汉语或者英语。

Dear Amy,

     My computer was broken so I couldn't read your two e-mails until today. I'm so sorry to hear about your

problems, 1. but I'm glad you're feeling better and are recovering, I'm amazed that in China someone's liver

matched yours！ 2. 这真是件令人感动的事-a stranger who donated part of his liver to a girl he doesn't even

know! You are right. We shouldn't be embarrassed about our weight. 3. I think you look great as you are, and

you're a wonderful person. I know that the pressure to stay slim is a problem, especially for an actress.

However, your mother knows best: 4. 没有什么比健康更重要.

     5. It's the same in China-many people, some of whom are not overweight at all, are always going on diets

or taking weight-loss bills. I hope they can learn from your story.

Love,

Zhou Ling

1.______________________________________________________________________________

2.______________________________________________________________________________

3.______________________________________________________________________________

4.______________________________________________________________________________

5.______________________________________________________________________________

我国从消灭了生产资料私有制，建立单一的公有制经济到确定“非公有制经济是我国社会主义市场经济的重要组成部分，”大约历经了

A．40多年

B．30多年

C．20多年

D．10多年

叙述钢锭中常见的宏观组织缺陷，消除或改善方法。

移植前多次输血，移植物存活明显延长可见于

A．肝脏移植
B．心脏移植
C．肾移植
D．骨髓移植
E．皮肤移植

在10月上中旬以（）在啤酒花田间的枯枝落叶、土缝、土块、杂草根际及棚架裂缝处群居越冬。第二年早春，气温达7℃左右时，越冬成螨出蛰，迁往已萌发的杂草上活动。

A、受精雌成螨

B、幼螨

C、卵

D、成螨