Children get tired of learning often because they _____ to do better than they can both at school and at

home.[ ]

A. hope        

B. are hoped      

C. expect        

D. are expected

关于力的下述说法中正确的是  [     ] 　

A． 力是物体对物体的作用，所以力总是成对出现的　

B． 由有一定距离的磁铁间有相互作用力可知，力可以离开物体而独立存在　

C． 有受力物体就一定有施力物体　

D． 力的大小可以用天平测量