Thefarmerhadtowearheavybootsinthewinterbecausethefieldsweretoowetand________.
Wemust______thattheexperimentiscontrolledasrigidlyaspossible.
Humanbehaviorismostlyaproductoflearning________thebehaviorofanimalsdependsmainlyoninstinct.
设函数f(x)在x=0处连续，下列命题错误的是（）
Abeamoflightwillnotbendroundcornersunless________(make)todosowiththehelpofareflectingdevice
