The answer is D, protein.
Protein is chains of amino acids.
For example, our body requires protein to function, but we cannot directly absorb the protein from the food. Instead, our body secrets enzymes protease to digest the protein and break them down into amino acids blocks. This is the basic form of protein
In opposite, carbohydrates is made up of simple sugars such as glucose. DNA is a double helix structure that makes up the chromosomes and they contain genes. Lipids are made up of 3 fatty acids and glycerol.
So, the answer should be D.
