Ted is such a helpful colleague that he is willing to do, ________， any favour we might ask him.

A．without question

B．in addition

C．as a result

D．on the contrary

挖掘机行驶时能实现原地旋转是因为：（）。

A.两条履带同时向前驱动

B.两条履带同时向后驱动

C.两条履带同时相后方向驱动

D.两条履带同时转向驱动