单选题 According to the passage, the risk of infection from airborne microorganisms would likely be greater during a ______.

【正确答案】 B

【答案解析】文章一开头就交代了细菌在干燥的空气中难以存活“The vegetative forms of most bacteria are killed by drying in air，”反之，潮湿的空气下，其较易存活，传染性也就越强。A条件下，不利于其生存；C，D条件文中未提到。