动点沿半径R=5cm的圆周运动,其运动方程为S=2t(其中S以cm计,t以s计),则动点的加速度的大小为( )

B、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1606896672384bf85ca74b4524d4b87d3daf9b59e213b.png">

C、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1606896689099d51df94bfa31408bb98212d88b5fcaf8.png">

D、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1606896714490313d58a6a3004b1b8dc68e6972e52e0d.png">