-----What has made him upset recently?
----- alone to face a troublesome milk case.
A. Left
B. Being left
C. Having left
D. To leave
网友回答
A. Left
(答案→)B. Being left
C. Having left
D. To leave
解析：考查动名词做主语。Being left alone to face a troublesome milk case实际上是句子的主语。句意：—最近什么事情让他难受？-被独自留下处理难办的牛奶案件让他难受。