I didn’t know  this years ago ,but recent science ____that inharmonic marital(婚姻的) life like quarrels or fights harms one’ heart.

A．showed

B． is showing

C．has shown

D．shows

作为学习动机的基本构成要素,能够激起有机体的定向行为,并能满足某种需要的外部条件或刺激物叫().