Here are the appropriate forms of the words to fill in the blanks:

1. (friend) **friends**
2. (health) **healthy**
3. (collect) **collecting**
4. (convenience) **convenient**
5. (safe) **unsafe**
6. (health) **health**
7. (tradition) **traditional**
8. (generous) **generously**
9. (sound) **soundly**

Here are the completed sentences:
1. I like to eat **with friends**.
2. Iceland is considered the most **healthy** country in the world.
3. My brother has been a **collecting** stamp for several years.
4. It is a/an **convenient** place to hold a picnic because it is too near the road.
5. Drinking water in some areas may be **unsafe** with several local farmers.
6. During my stay in the village, I was **health** is very important.
7. Encouraging children to eat and drink **health** is very important.
8. Local people in the village often wear their **traditional** costume during the festival.
9. Please give **generously** to that charity to help the homeless after the flood.
10. The baby slept **soundly** because the bed was really comfortable.

If you have further queries or would like to work on more exercises, feel free to ask!