When did you start to collect stamps?— I got my ______ stamp when I was ______ years old.

Did you finish your writing assignment(作业)?—Of course I did. ________, I have got an “A”.[ ]

How did you the money?-We helped an elementary school in our city.

Whose pen is this?— Oh, it’s_____. I was looking for it everywhere.

Air quality in our city is becoming worse and worse.—Yes. These days’ PM2.5 readings are frightening. We must do something to ______air pollution.