"what part of the antibody's structure determines its class? "

Out of the following given choices;
A) light (L) chain B) constant (C) regionC) variable (V) regionD) heavy (H) chain
The answer is B. This region is called the Fc region and composed of only heavy polypeptide chains only. It is used to classify antibody according to class. There are IgM, IgA,   IgG, IgE, and IgD. Fab is the varying region of the antibody that is significant in binding antigens.

Some of her  assignments would be creation of drugs. she is a medical chemist after all so she'd need to have the necessary knowledge to make medicine which can later be sold in a pharmacy