Here are the completed sentences using the past simple form of the verbs:

1. Alex **took** part in the Green Campaign last summer vacation.
2. They **joined** the volunteer club three years ago.
3. We **donated** glass bottles and jars to the recycling center yesterday.
4. I **did** a lot of volunteer work when I was in high school.
5. Luis **taught** as a volunteer language teacher at a local community center.
6. Volunteers **picked** up trash along roads, trails, and public spaces.
7. Samantha **bought** a ticket for the fair in her town.
8. A publishing company **sent** the books to the school library.
9. Student volunteers **taught** maths and English to street children last summer.
10. She **spent** her free time helping the elderly at the nursing home.