— 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 |
These students are quick at learning. We'll have them __________ with new methods.
| A．training | B．to train |
| C．to be trained | D．trained |
What he lacks is more patience,___________?
| A．isn't it | B．is it | C．doesn't he | D．does he |
I told him what I was surprised____________ his attitude towards his study.
| A．is | B．was | C．at is | D．at was |
The visiting Minister expressed his satisfaction with his talk,__________ that he had enjoyed his stay here.
| A．having added | B．to add | C．adding | D．added |
I just don't understand_______ that prevents so many Americans from being as happy as one might expect.
| A．why it does | B．what it does | C．what it is | D．why it is |