Answer:
The correct answer would be protein.
Explanation:
The given molecule is casein from the milk which is a protein. Proteins are build up of hundreds or thousands of smaller units known as amino acids linked to one another in long chains. The general chemical formula of a protein is RCH(NH2)COOH, in which R is a group termed as a side chain that varies in composition and structure.
The amino acid constitutes are carbon, oxygen, hydrogen, and nitrogen, other elements are found in the side chains of certain amino acids such as sulfur, phosphorus, and selenium.
thus, the correct answer is protein.