答案：A
下面所叙述的力，属于万有引力的是（ ）
A．马对车的拉力
B．地磁场对指南针的作用力
C．太阳对地球的吸引力
D．摩擦后的橡胶棒对小纸片的吸引力
— Hasn't the thief admitted his crime by now?
— No, ______ questioned many times. [ ]
A. if
B. though
C. unless
D. once
