單項(xiàng)選擇題(2011)-平面簡諧波的波動方程為y=0.01cos10π(25t-x)(SI),則在t=0.1s時刻,x=2m處質(zhì)元的振動位移是:()

A.0.01cm
B.0.01m
C.-0.01m
D.0.01mm