Can you tell me _________________ last night?

A．what was the matter outside

B．what was matter outside

C．what the matter was outside

D．what is wrong outside

房室交界处传导速度较慢的生理意义在于

A．有效防止出现期前收缩

B．有利于心房或心室同步收缩

C．有利于心室充盈和射血的交替

D．有效避免出现完全强直收缩