题目内容
No ________ of human habitation was seen．
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
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
