It looks like you're working on a grammar or language exercise that involves completing sentences. Here are suggestions for the blanks based on the context provided:

3. There are some chairs and a table in the kitchen.
**We have** some chairs and a table in the kitchen.

4. Not many people can understand his lecture.
**Only** a few can understand his lecture.

5. It is wrong of us to throw rubbish.
**We** should not throw rubbish.

6. It is necessary for us to be present at the class discussion on Saturday.
**We** must be present at the class discussion.

7. The tour guide tells us not to throw rubbish.
**The tour guide says that we** should not throw rubbish.

8. Don't drop litter.
**You** should not drop litter.

9. They don't allow children to travel alone.
**Children** are not allowed to travel alone.

10. Their rule is wearing a swimsuit in the pool.
**You** must wear a swimsuit in the pool.

Feel free to adjust any of the responses as necessary!