可兴奋细胞受到刺激后，首先可出现
A．锋电位B．阈电位C．负后电位D．局邮电位E．正后电位
参考答案：D
Distress traffic is the communication（）between the station in distress and the ships, aircraft, coast radio stations, coast earth stations and rescue centers participating in the rescue work.
A.exchange
B.to exchange
C.exchanging
D.exchanged
出口跟单托收的含义？
