Thêm từ vào để câu có nghĩa:
1.why/others/community/a/help/service/is/great/to
2.they/community/people/because/volunteer/want/improve/to/their
3.encouraged/books/people/street children/we/to/donate/and/clothes/to
4.what/to/help/we/can/do/the environment/clean?
5.work/done/you/ever/have/volunteer/any
6.free times/Joe/doing/work/spend/most/at/his/a/of/hospital/volunteer