— Do you think yesterday’s math problem was difficult?— Yes. I could           work it out.

一What do you think of Martin ?一He is the       boy in our class．He answers many questions and has created three clubs

Now the air in our town is __ than before. Yes. Something must be done to stop the pollution.

We know the boy ______.He likes the music________.

Don’t shout at him. He is unable to hear you because he is     .