建立下列复杂反射的正确顺序是( )(1)铃声响,狗就分泌唾液 (2)吃肉时,狗分泌唾液 (3)铃声成为条件刺激 (4)吃肉时,铃声响,狗分泌唾液 (5)多次反复
Don't ride too fast,David. the risk of an accident.( )
Take away
Write about
Think about
Try out
Tom and Jerry are very funny.I can't help when I watch them.( )
singing
laughing
sleeping
talking
Lucy is very young, she can live on her own.( )
and
or
so
but
I like the silence in the countryside.The city is too for me.( )
boring
large
crowded
noisy
It is Sunday.Let's just relax and enjoy .( )
myself
yourself
ourselves
Himself