当工件表面层温度超过相变温度，如果这时无冷却液，则造成（）。

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问题单项选择题

A.淬火烧伤

B.退火烧伤

C.回火烧伤

答案

参考答案：B

选择题

Only after being attacked by the Japanese in Pearl Harbor ___in the Second World War thoroughly.

A．had America involved

B．was America involved

C．America had involved

D．America was involved

判断题

分馏二中段回流主要作用是回收高温位能量，视情况可以不用。