第18题: [单项选择]接触麻疹后，何时采取麻疹被动免疫措施有预防麻疹的作用（） A. 立即 B. 3天内 C. 5天内 D. 7天后 E. 10天后 参考答案:C 答案解析:接触麻疹后5天内立即给予免疫血清球蛋白0.25ml/kg，可预防麻疹发病；超过6天则无法达到预防效果。
第19题: [单项选择]{{B}}Questions 11 to 18 are based on the conversation you have just heard.{{/B}} A. He wants it cooked sufficiently. B. He wants it cooked all the way through. C. He wants it not sufficiently cooked. D. He wants it cooked to a solid consistency. 参考答案:C 答案解析:[听力原文]
M: Would you like your steak rare, medium, or well-done
W: I’d like it medium. My husband
A. to cover the houses and fields B. for people to have the right amount of water at all times C. to help crops grow better D. to form a large lake 参考答案:B 答案解析:从第二段开头可知，为了解决上述问题，可以在河流上修建水坝，使之能旱季储水，雨季蓄洪。也就是说，使人们总是能有适量的水。[C]为干扰项，修建水坝并不止对农作物起有利的作用。
