Answer:
A. unexpected change in odor
Explanation: Common physical changes include melting, change of size, volume, color, density, and crystal form. Example the classic baking soda and vinegar reaction provides evidence of a chemical change due to the formation of a gas and a temperature change.
Purines are adenine and guanine. So the answer should be D (Pyrimidines). besides, phosphate group and pentose sugar are a part of a nucleotide.
