fill in the blanks with the suitable article a,an,or without article 1. thermostat,2wire

1. a
2. a
3. an
4. - (no article)
5. -
6. a
7. a
8. an
9. a
10. a
11. -
12. an
13. a
14. a
15. an
16. -
17. an
18. an
19. an
20. -