在切断刀主切削刃上磨凹槽可起到()和()作用。
参考答案:消除振动;导向
When I reached home, my husband was lying on the floor, ________ the kids with toys.
A.to entertain
B.entertains
C.entertaining
D.entertained
急性心包炎在我国最常见的病因是()
A.结核性
B.风湿性
C.非特异性
D.化脓性
E.病毒性