WT—50钻机取力时应先(),再进行下一步操作。
A.摘掉前桥
B.变速杆置于空挡
C.摘前后桥
D.扳动取力手柄
参考答案:C
I _____ home for a week up to now.[ ]
A. have returned
B. have been back
C. returned
D. were
可以在食品加工中添加食品添加剂以外的非食用化学物质。