The rivers will become dirtier and dirtier        we take action to protect them.

      we’re late for the lesson, the teacher will get angry.

If there        no buying and selling of animals, there       no killing in nature.

If she        New York this afternoon, I        New York, too.

If they go to the party, they      .

Something        if they have the party tomorrow.

—Do you know if we will go for a picnic this Saturday?
—I think we will if we        any classes.

We will go for a picnic if it        tomorrow.

You may answer it easily if you choose another question.
本句是一个包含主句和从句的主从复合句，其中you may answer it easily是      。

If it doesn’t rain tomorrow, we’ll go to the park.
本句是一个包含主句和从句的主从复合句，其中if it doesn’t rain tomorrow是      。