当排量一定时螺杆钻具的压力降随钻头负荷的增加而增加。
参考答案：对
If hehis legs yesterday, he _______ the Summer Palace with us now.
A．hadn’t hurt; would visit
B．hadn’t hurt; would have visited
C．didn’t hurt; would visit
D．didn’t hurt; would have visited
面部的主要凹陷是（）。
A、颧结节
B、眉弓
C、脸颊沟
D、颞线
