One word Substituion

1. A person residing in a country of which he is not a citizen=Alien
2. Absence of government = Anarchy
3. Happening every year = Annual
4. That does not bear the name of the writer = Anonymous
5. That which counteracts putrefaction=Antiseptic
6. Living in water = Aquatic 
7. One who does not believe in god = Atheist
8. An assembly of hearers= Audience
9. The life story of a person written by himself = Autobiography
10. One who pursues some art or sport as hobby = Amateur 
11. Signature of some important person in his own hand = Autograph
12. One who cannot pay off his debt= Bankrupt
13. The life story of a person = Biography
14. Liable to be easy broken = Brittle 
15. The science of vegetable life = Botany