Parallel and gradual increase (the more...).

1. The boy is getting _________ .

2. The _________ it rains, the sadder I feel.

3. The older you get, the _______ you'll feel.

4. The more you work, the ________ free time you'll have.

5. There are ________ people in the world.

6. The _________ problems you have, the happier you'll be.