Answer:
C. Protein
Explanation:
Proteins contain C, H, O, and N.
Most notably, they contain an R group (aka a side chain), which is different for each for amino acid. The R group is symbolized by the letter R in the image.
Answer:
A common measurement system allows them to make direct comparisons instead of having to know things like how much a certain animal weighs.
Explanation:
Got it off goo gle
C, when mutations are not always predictable they are random
D would be the correct answer