The old couple have been married for 40 years and never once _______ with each other.

A．they had quarreled

B．they have quarreled

C．have they quarreled

D．had they quarreled

击球力量与以下因素有关：

⑴（）

⑵击球时球拍接触球的位置

⑶击球人的爆发力有大小

A、击球时力量

B、击球时挥拍速度

C、击球点的前后

D、击出的球点的高低