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问题 名词解释

对接接头

答案

参考答案：

两部件表面构成大于或等于135°，小于或等于180°夹角的接头。

名词解释

市场营销组合
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单项选择题

In ______ English became a formal requirement for the college entrance examination in China and began to appear in the curriculum for the 4th and 5th year of primary schools.

A．1952

B．1962

C．1972

D．1982
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