谁能给我用“an”来修饰的英语单词?

1.an hour
2.an American
3.an answer
4.an Russian
5.an recommendation
6.an offer
7.an explanation
8.an reason
9.an rule
10.an respecter
11.an result
12.an assumption
13.an image
14.an imagination
15.an octopus
16.an element
17.an idol
18.an effect
19.an upshot
20.an reflection
21.an representation
22.an ambulance