Here are the correct forms of the words to complete the sentences:

1. **documentary**
2. **threatening**
3. **global**
4. **practically**
5. **help**
6. **organization**
7. **advertisements**
8. **acceptable**
9. **hopes**
10. **technological**

So the completed text reads:

John watched a **documentary** on TV last night. It was all about the problems **threatening** our environment. He was shocked to find out how little he knew about **global** warning or acid rain. He had heard the term before but he knew **practically** nothing about the damage they cause to our planet. He feels he should do something to be of **help**. He would like to join an **organization** but he doesn't know which one to join. He has seen so many **advertisements** in newspapers that he can't make up his mind. However, he believes that it is **acceptable** not to be environmentally aware and he is **hopes** that one day everyone will be part of a world movement to save the earth. He was sure that in this time of **technological** advances, we find some way to solve the world's problems.