It is hard for me to imagine what I would be doing today if I in love at the age of seven

问题补充：

It is hard for me to imagine what I would be doing today if I in love，at the age of seven，with the Melinda Cox Library in my hometown.

A. wouldn have fallen

B. had not fallen

C. should fall

D. were to fall

答案：

A. wouldn have fallen

(答案→)B. had not fallen

C. should fall

D. were to fall

解析：

根据句意和I would be doing可以判断这是虚拟语气。at the age of seven是表示过去的时间状语，if从句中的谓语要用had not fallen，表示对过去情况的假设。