立式车床分单柱式和双柱式两种。
参考答案：对
The student asked her professor if he would have gone on the space ship he did know earlier.
A．if he knew
B．if he knows
C．he had known
D．had he known
采用混凝土小型空心砌块砌筑墙体时，水平灰缝砂浆饱满度不应低于（）％。
A、75
B、80
C、85
D、90
