题目

I'll come ________ to the point—if you want to make progress in English, you have to try to enlarge your vocabulary and use them frequently. A . officially B . actually C . straight D . entirely 答案：C在水平面上,小猴拉着小滑块做匀速圆周运动,O点为圆心，能正确地表示小滑块受到的牵引力F及摩擦力Ff的图是（       ）