—Mary looks down today.What is up?—Well,________happened between Mary and me is none of your business.
There are lots of plastic bags ____ in the river, ____ it very dirty.
--- Would you mind if I used your bike? --- ____.
The president spoke at the business meeting for nearly an hour without ____ his notes.
David worked hard at his lessons ____ he gained high grades in the exams.
As a young man, Zhou Enlai ____ the students movements and later ____ the Communist Party of China.