—I (come) to your office and didn't see (you).

The Earth gets s now. In some cities, the air is dirty. There are many cars in these cities. The s from cars makes the air very dirty. So we should s driving more cars. We should walk or ride bikes more often to school or the work place. Walking is a good way to k the air clean. It also makes us h and strong. Let's do more things to make the air clean.

Many people are waiting for the train. Some are reading books and some are saying goodbye to their friends. Mr Wang, Mr Li and Mr Green are talking so happily that they don't know the train is leaving (出发). The guard says to them, "Hurry up! The train is leaving." The three men hear the guard. Two of them jump onto the train quickly before it moves. Mr Wang is left behind. He looks very sad. The guard says to him, "Don't feel sad. The next train will come in ten minutes." "I know," Mr Wang says. "It's my train. My friends only come to say goodbye to me."