－What made little Tony so unhappy and cry in his room?                      

－____to go hiking with his brother.   [ ]

A．Having not been allowed

B．Not having allowed    

C．Having not allowed    

D．Not having been allowed

关于摩擦力与弹力的关系，下列说法中不正确的是（）

A.接触面间有摩擦力就一定有弹力

B.接触面间有弹力但不一定有摩擦力

C.摩擦力的大小总是与弹力的大小成正比

D.摩擦力的方向总是与物体运动方向相反