1.

1. hop
2. hopping
3. hoping
4. humming

2.

1. boiling
2. toiling
3. chopping
4. cutting

3.

1. will
2. should
3. may
4. can

4.

1. unsettling
2. unbelievable
3. unworking
4. understanding

5.

1. to
2. for
3. up
4. in

6.

1. age
2. ages
3. aged
4. ageing

7.

1. exercise
2. dance
3. repeat
4. run

(Reference keys.)