A（）computer is a personal computer whose hardware is capable of using any or all of the following media in a program: audio, text, graphics, video and animation.

A．database

B．multimedia

C．network

D．mainframes

下列说法中正确的是（　　）

A．支点到力的作用点的距离称为力臂．

B．杠杆平衡就是指杠杆处于静止状态．

C．动力作用点离支点越远，一定越省力．

D．力使物体转动的效果决定于力和力臂的乘积．