One key difference between carbohydrates and proteins is: the carbohydrate molecule lacks nitrogen. the protein molecule contains more stored energy. the carbohydrate molecule is in butter. only the protein molecule contains iron. only the carbohydrate molecule can form long chains.

Option A, the carbohydrate molecule lacks nitrogen

Explanation:

Carbohydrates are group of organic compounds that contain three essential elements -

a) carbon

b) hydrogen

c) oxygen

While a protein is polymer of amino acids. An amino acid consists of following essential components

a) An amino group (−NH2) that has nitrogen molecule

b) An acidic carboxyl group (−COOH)

c) An organic R group that primarily has CHO elements

Hence option A is correct

well, i believe that the answer is 2. : 3