Which of the following structures represents a protein?
A monomer made up of a nitrogenous base, a five carbon sugar, and a phosphate group bonded together.
A monomer with an amino group, carboxylic acid, hydrogen atom, and R group bonded to a central carbon atom.
A monomer with the formula C6H12O6. Five carbon atoms and one oxygen atom form a hexagonal ring, with the other atoms bonded to that ring.
A molecule made up of four carbon rings with other atoms bonded to those rings.