Fresh air is good ____ your health.
I had been puzzled over the problem for over an hour without any result, ____ all at once the solution flashed across my mind.
On the third floor there are two rooms, ____ is used as a meeting-room.
---Does ____ of the two foreigners work in Chengdu? ---Yes.____ of them have been working here as English teachers for three years now.
Bill, often regarded as one of the best students in his class, ____ to be the student who cheated in the exam.
This pair of shoes doesn't look good, but that pair is ____ better, I think.