问题补充：
My father worked day and night. Otherwise, there no one to support the family.
A. would be
B. must be
C. would have been
D. must have been
答案：
A. would be
B. must be
(答案→)C. would have been
D. must have been
解析：从信息词 Otherwise可以看出是一个含蓄条件句，再从动词worked 可以看出是与过去相反，故主句使用would have been。本句可以改写为if引导的条件状语从句：if my father hadn’t worded day and night,there would have been no one to support the family.
