下列物质用途错误的是[ ]
A.
B.
C.
D.
答案：A
Both Lucy and Lily prefer ______ to______ at school. [ ]
A．dance; sing
B．dancing; singing
C．to dance; singing
D．dancing; sing
A．角速度为0.5 rad/s
B．转速为0.5 r/s
C．轨迹半径为 m
D．加速度大小为4π m/s2
m