Do you know what ___ while you were away from home?

A．had happened

B．was happened

C．has happened

D．happened

动作电位的"全或无"特性是指同一细胞动作电位幅度（）

A、不受细胞外Na+浓度影响

B、不受细胞外K+浓度影响

C、与刺激强度和传播距离无关

D、与静息电位无关