It said the country's confirmed H7N9 cases were isolated and there has been no______ of human-to-human transmission.

A．mark

B．symbol

C．sign

D．signal

其临床分期是

A．Ⅰa期

B．Ⅰb期

C．Ⅱa期

D．Ⅱb期

E．Ⅲa期