Theboyranoutoftheclassroomwithouttheteacher's_______.
A、commandTostudyaforeignlanguage,__________.
Whenworkersareorganizedintradeunions,employersfindithardtolaythem________.
Be careful, _______ you'll fall down.
Human behavior is mostly a product of learning ________ the behavior of animals dependsmainly on instinct.
Theassociationis________toraisingfundstohelptheblind.
