题目内容

电火花线切割称为()

A. WEDM
B. EDM
C. ECM
DEM

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用电火花机床不能加工的形状或材料为()。

A. 盲孔
B. 圆孔
C. 上下异形
D. 淬火钢

The house _______ many years ago.

A. is built
B. was built
C. has been built
D. had been built

The article __________ many times.

A. has been written
B. was written
C. wrote
D. write

You ________ clean that room. It is very clean now.

A. must
B. have to
C. need to
D. don’t need to

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