---Did a letter come for me?

---Yes, ____ came for you when I was on the point of going out this morning.

A．that

B．it

C．one

D．this

.能实现空间任意两轴的传动，也可实现回转运动和直线运动之间的转换，具有工作可靠，传动比恒定等特点的是（）传动方式。

A.带

B.链

C.齿轮