---What do you think of teaching , Bob? ---I find it fun and challenging. It is a job ___you are doing something serious but interesting
The changes in our chemistry lab will cost quite a lot, ____ they will save us money in the long run.
Living things are dying out quickly. Let’s ask ____ destroying them in the past years.
____ that I’m feeling all right, my brain is also beginning to work much better.
The workers were making so much noise in the workshop, and the boss hurriedly went to see ____.