In the Laboratory Analysis for Amphetamine Using Antigen and Antibody

In the laboratory analysis for amphetamine using antigen and antibody interactions as the basis for measurement, there is concern of cross-reactivity with the over-the-counter drug pseudoephedrine.What is the basis for this concern?

A) Pseudoephedrine may have a similar antigenic determinant site as amphetamine, since their chemical structures have some similarity.
B) Pseudoephedrine may block the weak, noncovalent forces that operate between antigen and antibody.
C) Pseudoephedrine may react with amphetamine to produce a product that is not recognized by the antibody.
D) Pseudoephedrine and amphetamine will not fit into the antibody-binding site at the same time.