问题
选择题
--- What has made him upset recently?
--- __________ alone to face a troublesome case．
A．Left
B．Being left
C．Having left
D．To leave
答案
B
题目分析：句意：--什么使他最近不安？--被单独留下面对棘手的情况。因为问句是what…?对主语提问，所以回答的是主语的内容，用动名词做主语，he和left是被动关系，用动名词的被动做主语，选B。