{$mEDiAurl}
whAt DoEs thE proFEssor imply ABout thE iDEA oF A CritiCAl pErioDA．it is A notion thAt is hArD to DEny in light oF rECEnt EviDEnCE.
B．it is not rElEvAnt to ChilDrEn who grow up unDEr normAl ConDitions.
C．thE notion is irrElEvAnt to lAnguAgE lEArning ExCEpt in FErAl ChilDrEn.
D．thE iDEA is hArD to provE DuE to thE ovErABunDAnCE oF FErAl ChilDrEn.