—It smells terrible. What has happened here?—Look, there is much waste gas _____ from the chemical factory.
Our hometown ________________ a lot in the past ten years.
The teacher asked _______________.
We are very tired after a long walk. Let’s stop_________ a rest.
_______ it rained heavily, ________ all the students came to school on time.
We are looking forward to ____________ the Great Wall.