Answer:
These are my reasons, I don't know if you need others...
1. soy (describe where the person is from)
2. está (describe where the pencil is)
3. es (describe the nationality of the grandmother)
4. están (describe a feeling)
5. estás (describe where someone is)
6. es (describe the dog)
7. estamos (describe where we are)
8. es (describe the location of the party)
9. son (tell time)
10. es (describe what color my favorite blouse is)
