用所给动词的适当形式填空。

1.  Don't forget ______ (turn) off the lights after school.

2.  She would rather    ____ (learn) French than Japanese.

3.  The old man is too old   ___ _ (walk).

4.  Not______ (get) enough sleep has serious effects on our brain's ability to work.

5.  His father didn't allow him ______ (watch) TV on weekends.