— The woman biologist stayed in Africa studying wild animals for 13 years before she retur

问题补充：

— The woman biologist stayed in Africa studying wild animals for 13 years before she returned.

— Oh, dear ! She a lot of difficulties !

A. may go through

B. might go through

C. ought to have gone through

D. must have gone through

答案：

A. may go through

B. might go through

C. ought to have gone through

(答案→)D. must have gone through

解析：此句是对已经发生的事情的肯定的猜测，故排除A、B。根据句意，排除C。故答案为D。