Which factor causes the main difference in chemical properties between different amino acids?

Question

Quizplus · Accepted Answer

The R group (or side chain) is different for each amino acid, leading to variation in chemical properties. Some R groups are polar, some are nonpolar, and others are charged, causing differences in solubility, reactivity, and other chemical behaviors.

Answer: A, B, D, E are incorrect 
 Although the amine and carboxylic acid groups are important components of all amino acids, they are constant and do not contribute to the differences in chemical properties between amino acids. Molecular weight may affect physical properties such as solubility, but does not significantly impact chemical behavior. "None of the above" implies that there is no primary factor contributing to the difference in chemical properties, which is not the case.

Which Factor Causes the Main Difference in Chemical Properties Between