II)

1.organisation

2.homeless

3.elderly

4.encourages

5.neighbourhood

6.environmental

7.donated

8.benefited

9.disabled

10.volunteer

III)

1.have offered

2.cleaned

3.recycled

4.tutors

5.Did you provide

6.has donated

7.Has Tom participated

8.didn't start

9.Do your friends sing

10.haven't finished

IV)

1.They are very dirty because we haven't completed cleaning up the streets yet.

2. The children do not have enough warm clothes because their families are very poor.

3. We talk and sing for the elderly people because it makes them happy.

4. We provide evening classes for street children because they do not have opportunity to go to school.

5. You should recycle rubbish because it helps protect the environment.