it CAn BE inFErrED From thE stAtEmEnt ABout mothEr ChimpAnzEEs AnD thEir young (linEs 21—23) thAt young ChimpAnzEEs hAvE DiFFiCulty ______.
A．CommuniCAting with thEir mothErs
B．ADDing quAntitiEs
C．mAking ChoiCEs
D．opEning hArD nuts