题干
Only when Tom fully recovered______back to work.
A：did he go
B：he went
C：had he gone
D：he had gone
答案(点此获取答案解析）
A
A：did he go
B：he went
C：had he gone
D：he had gone
与
是定义在同一区间
上的两个函数，若对任意
，都有
成立，则称
与
在