The river will be dirtier and dirtier________we do nothing to protect them.
---- Please don’t smoke here. Look at the sign. ---- ________.
-_______is the old bridge over the river?- Not very wide. It's about three meters.
We didn’t find________ in the picture.
- _______ exercising, and you'll be healthier.
----When did you _________ Suzhou last night?----At about 9 p.m.