Molecules of proteins contain
A) Carbon
B) Nitrogen
C) Oxygen
D) All the above

Hint: A molecule is defined as two or more different element atoms of the same element, which are bound together.

Complete Answer:
Protein is one that often springs up in healthy eating discussions. We are advised to eat proper amounts of protein besides carbohydrates and fats, to have a healthy diet. Protein-Rich Foods, protein is a molecule type that forms part of any living organism. Protein molecules, for one thing, are structural building blocks within an organism. Protein molecules participate in metabolism in the body.
We've already proven that protein is a molecule. In particular, it is an organic molecule. But that doesn't mean organic in the sense of being naturally grown without pesticides. Organic to be precise, refers to carbon-containing compounds. Zeroing in at the molecular level, we can see that proteins consist of atoms such as carbon, hydrogen, oxygen and nitrogen. These atoms bond to form molecules. And the molecules fit together to form the protein subunits, which are called amino acids. Amino acids are the basic constituent elements of protein molecules. They make up a proper protein when they are linked together in a particular order. There are twenty amino acids in all, but it is the types and sequences of these subunits that make the great variety in protein molecules possible. Peptide bonds are joined to amino acids. The completed chain is therefore termed a polypeptide.

So the correct option is D i.e All the above.

Note: In living organisms, protein molecules are huge organic molecules. They serve a wide range of functions including structure, conveyance and defence.