Acetylcholine使窦房结细胞auto-rhythmicity降低是通过

Acetylcholine使窦房结细胞auto-rhythmicity降低是通过
A.maximal repolarization potential减小
B.threshold potential水平上移
C.If电流降低
D.膜对K+通透性增大
正确答案：膜对K+通透性增大