A stands out most to me, CO comes from the air and air is basically oxygen we breath. When we exhale CO comes out (of course). I would say A is correct.
The answer would most likely be C
Nucleotides is the answer: they have a phosphate group, a deoxyribose sugar, and a nitrogenous base.
The phase of mitosis where the chromosomes coil up and condense is at prophase.
