1) If he (learn) the rule, he (be) able to do the exercise. 2) It (be) difficult to do the task unless you (listen) to the teacher.

3) If people (have) flying cars in future, there (be) less air pollution.

4) If people (use) their cars less, they (not create) traffic jam.

5) Our life (not change) for the better if people (pollute) the environment.

6) Unless it (rain), we (go) for a walk.