目前东风4型机车大修时柴油机普遍使用（）材料的活塞。A、锻铝 _爱下问搜题

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问题单项选择题

目前东风4型机车大修时柴油机普遍使用（）材料的活塞。

A、锻铝

B、铸铁

C、钢顶铝裙

D、钢顶铁裙

答案

参考答案：D

选择题

The teacher, along with his students, _____ experiments in the laboratory when the explosion happened.

A. were doing
B. have been doing
C. was doing
D. had done

选择题

—The wind is always blowing here．

—How I wish it ______ today

A．won't blow

B．didn't blow

C．doesn't blow

D．isn't blowing