Here are the complete sentences based on the given words:

1. Are you interested in festivals? - Yes.
**Yes, I am interested in festivals.**

2. Did Jim buy the cake yesterday? - No.
**No, Jim did not buy the cake yesterday.**

3. Did James spend his last summer in Italy? - No.
**No, James did not spend his last summer in Italy.**

4. Did Mary visit Jim and Jane yesterday? - Yes.
**Yes, Mary visited Jim and Jane yesterday.**

5. Did David start collecting stamps 3 years ago? - Yes.
**Yes, David started collecting stamps 3 years ago.**

6. Will people hold a festival next spring? - Yes.
**Yes, people will hold a festival next spring.**

7. Were you ill yesterday? - No, but I decided to skip class.
**No, I was not ill yesterday, but I decided to skip class.**

8. Did you buy a lot of apple juice last week? - No.
**No, I did not buy a lot of apple juice last week.**