_______ in thought, I didn’t notice what was happing.
_______ has recently been done to provide more buses for the people, a shortage of public vehicles remains a serious problem.
When a giraffe has ______ drink, it has to stand with its front legs wide apart in order to reach ______ water easily.
If we ___________some measures, we might have prevented the environmental pollution.
–May I smoke in the room? --No, you______________. It’s a non-smoking room..
---It’s a long time ______ I last saw you. ---Yes, and it will be another month ______ we can meet again.