记者要为4名志愿者和他们帮助的1位老人拍照,要求排成一排,且老人必须排在正中间,那么不同的排法共有 [ ]
A.120种
B.72种
C.56种
D.24种
答案:D
---What did you do yesterday?
---My brother took two friends of _______ to play chess with us. But I don’t know
________ of them.
A.his; all
B.him; both
C.his; either
D.him; neither
简述FOCKE401/408包装机压缩空气压力不足故障的检查方法。