{$mEDiAurl}
why DoEs thE proFEssor mEntion thE ExprEssions "mothEr tonguE" AnD "mothErEsE"A．to provE thAt mothErs ArE BEttEr lAnguAgE rolE moDEls thAn FAthErs.
B．to illustrAtE how pArEnts proviDE A support systEm For lAnguAgE lEArning.
C．to CompArE normAl spEECh pAttErns with thE BABy tAlk thAt pArEnts usE.
D．to ArguE thAt sEConD lAnguAgE lEArning is morE DiFFiCult For ADults.