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

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：该题考查情态动词的用法。情态动词+have done表示对过去的推测。句意为:“为研究野生动物,这个女生物学家在回来前在非洲待了。”“哦！她一定克服了许多困难。”