B.Translate the following underlined sentences into English
专家提醒说, 雾对人体健康的危害有很大的隐蔽性。据测定， 雾滴中各种酸、碱、 盐、胺、酚、尘埃、病原微生物等有害物质的比例，比通常的大气水滴高出几十倍。
【正确答案】：
EXPERTS CAUTION THAT THE HARMFUL EFFECT OF FOG ON OUR HEALTH IS OFTEN CONCEALED. 
【题目解析】：本题考查单句的翻译——词义的选择。“隐蔽性”译成被动结构，sth. is concealed。主谓宾结构的翻译。Experts caution that the harmful effect of fog on our health is often concealed.