Food safety is important. Rules____ to stop people from food pollution.

—People find it hard to get across the river．—I think at least two bridges         over it．

--- Listen! David is talking happily with his mother in the next room.　--- It ______ be his mother. She has gone to Yunnan to be a volunteer doctor.

When he was there, he ______ go to that coffee shop at the corner after work every day.

I ________ be a little bit slow, but at least I don’t make stupid mistakes.