I got this answer wrong, can someone please explain why this answer is A.) Antigenic determinants reside only in the var

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I got this answer wrong, can someone please explain why thisanswer isA.) Antigenic determinants reside only in the variable region ofthe light chains.
Which of the following is NOT true of immunoglobulinmolecules?
A. Antigenic determinants reside only in the variable region ofthe light chains.
B. They consist of four polypeptide chains held together bydisulphide bridges.
C. Some are membrane bound.
D. Proteolytic cleavage can generate fragments containing theantigen-binding site.
E. They have two identical heavy chains and two identical lightchains.