英语周报 @@@@@@@@@@答案

10.参考答案BCD说明分析根据二项分布的数学期望和方差的公式,可得E(X)=np=30,D(X=np(1-)=20,解得p=3,所以A错误;根据数据方差的计算公式可知,将一组数据中的每个数据都加上同一个常数后,方差恒不变,所以B正确;由正态分布的图象的对称性可得P(-1≤0-1-2212=2-,所以C正确由独立重复试验的概率的计算公式可得,P(X=k)=C0(0.8)(1-0.8)10一k,由组合数的公式,可得当k=8时取得最大值,所以D正确所以正确的命题为BCD

书面表达One possible version:Dear PeterI'm writing to invite you to attend a lecture about exercise and health in our schoolAs you know, there are many students who are overweight or short-sighted in our school. They devote all their energy to studying andignore exercise. As a result, they are not so strong and healthy as they should be. Besides, some girls choose to keep slim by controlling thdiet, which also affects their health. So we hope to promote some health knowledge through this lecture: The lecture, which is to be held in theschool hall next Friday afternoon, will last from 3: 00 pm to 5: 00 pm. I hope you can attend it and share something with us.ooking forward to receiving your early replyYours sincerely

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