1. Neither do I/ I don't, either
2. My brother did, too/ So did my brother. 
3. We are, too/ So are we. 
4. They won't, either/ Neither will they.
5. His parents weren't, either/ Neither were his parents
6. Her sister can, too/ So can her sister.
7. Ba didn't, either/ Neither did Ba
8. Her aunt does, too/ So does her aunt
9. These bananas aren't, either/ Neither are these bananas
10. His children do, too/ So do his children
11. Her little cousin does, too/ So does her little cousin 
13. My secretary couldn't, either/ Neither could my secretary
14. The vegetable aren't, either/ Neither are the vegetables
12. His coleages may, too/ So may his colleages
15. I did, too/ So did I
16. They shouldn't, either/ Neither should they
17. Your elder brother shouldn't, either/ Neither should your elder brother
18. Hers are, too/ So are hers
19. French is, too/ So is French
20. Those ones did, too/ So did those ones

1. c
2. b
3. b
4. c
5. c