联轴器故障及损坏情况有哪些:()
A.联轴器体内有裂纹
B.联轴器连接螺栓孔磨损
C.齿形联轴器轮齿磨损或折断
D.齿轮套键槽磨损
参考答案:A, B, C, D
以下各项中,不是细菌的是( )
A.乳酸菌
B.硝化细菌
C.大肠杆菌
D.酵母菌
We have been in China three years. We like it very much.
A. in B. since C. for