He has written a lot of books, but ______ good ones.
After his journey from Beijing during the National Day, Tom returned school, __________.
---The light was on all night long. ---Yes. It seemed that Mike ________. He was the last one to leave the office.
He became inspired when he thought about helping ordinary people _________to cholera.
At first, my new surroundings were difficult _________
There is a system ________the waste is disposed of using the principles of ecology.