Choose a or an

1. [a|an] umbrella
2. [a|an] orange
3. [a|an] book
4. [a|an] guitar
5. [a|an] elephant
6. [a|an] notebook
7. [a|an] fish
8. [a|an] yo-yo
9. [a|an] mouse
10. [a|an] giraffe