Why Can't Your Body Produce Proteins from Carbohydrates and Fats

Why can't your body produce proteins from carbohydrates and fats alone?

A) Because the amine group of an amino acid has to have a nitrogen atom.
B) Because the side group of an amino acid has to have an oxygen atom.
C) Since the fats are made of nonpolar structures, they cannot combine with the carbohydrates to form proteins.
D) Because the carboxylic acid group must have a nitrogen atom.