Humanbehaviorismostlyaproductoflearning________thebehaviorofanimalsdependsmainlyoninstinct.
A、soInthefuture,more______shouldbeplacedontheeducationoftheyoung.
SinceWilliamhadbeenseriouslyillforseveralmonths,hisparentswereworriedabout________toreturntoschoolfull-time.
Thestudentfoundthenovel_______.Itprovidedhimwithsomuchinformationaboutthesubject.
Itisusefultoscience_______theearthasanobjectinspace.
Becareful,_______you'llfalldown.
