Answer:
I am positive the answer is C because I used to study the exact same lesson.
Answer:
7. Adenine (A), nitrogenous bases
8. cytosine
9. nucleotides
10. purine
11. double helix
12. genetic material
13. single-ring
14. double-ring
15. nucleic acids
16. chromosome
Hope this helps :)
P.S. plz ask if you need any clarification
Very simply, I think that they may block the sun's rays from reaching the Earth, cooling down the planet, or they may eventually end up being turned into acid rain and rain back down to the Earth.