初侵染和再次侵染
参考答案：前者指由越冬菌原引起的第一次侵染，后者指由初侵染引起的所有侵染
We are not born with courage, but_____ born with fear.
A．we are neither
B．neither are we
C．we neither are
D．neither we are
慢性心房纤颤是指心房纤颤病史（）
A.大于24小时
B.大于48小时
C.大于3天
D.大于1个月
E.大于3个月
