铸圈的衬垫要求在铸圈的上下端形成3～5mm空白区，主要作用是（）

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问题单项选择题

A.起分离作用

B.防止铸型从铸圈中脱出

C.为了美观

D.为了减少膨胀

E.以上都不是

答案

参考答案：B

阅读理解

阅读短文，判断正(T)误(F)。

Dear friends,

I am Nancy. I am from America. I can speak Chinese. I like travelling best. I want to go to Australia

by plane. I send e-mails to my friends in Australia once a week.

( ) 1. Nancy is from America.

( ) 2. She can speak Chinese.

( ) 3. She wants to go to Australia by ship.

( ) 4. She sends e-mails to her friends twice a week.

单项选择题

在产品价值评价时，若A、B、C、D四种零件的价值系数分别为V_A＝0.5、V_B＝0.8、V_C＝1、V_D＝ 1.2，则应重点研究的对象是( )。

A．A

B．B

C．C

D．D