功率是表示物体____的物埋量。一个50N的力在作用某物体时,力方向上移动速度是40cm/s,则这个力的功率是____。
做功快慢,20W
分层保险的定义是什么?
Though they are______little children , they have worked out _______many difficult math problems.
A.so; so
B.such; such
C.so; such
D.such; so