My friend, David, was not used __________by air, so he felt unwell.

Her lecture ______ all the recent developments in the subject, which will attract more people.

More are ________ in the countryside when their parents floodinto the cities for jobs.

You should be more confident in______ situation is challenging you.

.If you want to be thinner and healthier, you’d better eat_______food and take______ exercise.