轴承的主要作用是()。
A.支承轴
B.传递运动
C.传递动力
D.减少摩擦
参考答案:A
He insisted that he______ his best and ______ rewarded.
A.had done, must be
B.did, must be
C.do, should be
D.had done, be
Unix系统全部是开源的。()