Disease Associated with Immune System - Medical Science

Q1:

A monoclonal antibody (mAb) specific for the 2,4-dinitrophenyl (DNP) hapten might also bind

A Leu or Ileu

B His or Pro

C Tyr or Phe

D Ser or Thr

ANS:C - Tyr or Phe

May I know how the mAb specific for 2, 4-dinitrophenyl (DNP) hapten might also bind to Tyr or phe?