◎ 题干
It said the country's confirmed H7N9 cases were isolated and there has been no______ of human-to-human transmission.
A.markB.symbolC.signD.signal
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“It said the country's confirmed H7N9 cases were isolated and there has been no______ of human-to-human transmission.A.markB.symbolC.signD.signal…”主要考查了你对  【可数名词及其单复数】【集合名词】【名词】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。