如用一夹一顶装夹工件，当卡盘夹持部分较长时，相当于（）支撑点。
A.两个
B.三个
C.四个
D.五个
参考答案：C
—Hi, Tommy. Are you busy now?
—________. I have done my work, and I’m going out for shopping.
A．Don’t mention it.
B．Nothing serious.
C．Never mind
D．Not really.
妊娠初期，每月仍有少量月经而无损于胎儿者，称为（）
A.暗经
B.居经
C.垢胎
D.胎漏
E.暗产
