(EvEn though) hE (hAD BEEn stuDying) English For thrEE yEArs (BEForE) hE CAmE to EnglAnD, it is still DiFFiCult For him to mAkE himsElF (unDErstAnD).
A．EvEn though
B．hAD BEEn stuDying
C．BEForE
D．unDErstAnD