英语周报高一2017-2018 46期答案

13.1(2分)0.993分)由题意可得,抽到二等品的件数符合x正项分布,即XB(10000),由二项分布的期望公式可得E(X)=mp=100×0.01=1,D(X)=np(1-)=100×0.01×试登,O一水因,0p=(0p严0.99=0.99

【参考范文】One day, Spotty returned from his daily walk with a broken leg. Appearing exhausted, he came to myroom and sat near me, the leg bleeding. I called my mother and she quickly tied a bandage around his leg andgave him food to eat. I was very upset. But the next day, Spotty followed me wherever I went happily asusual though he limped a bit. After this incident my relation with Spotty became more intense. I reallyadmired him a lot for his courageAlmost a year later, one midnight we heard Spotty barking breathlessly. We rushed out and saw himbarking continuously, heading somewhere. After some time Spotty became quiet. I patted him on his backand came inside. The next morning, my heart skipped a beat when I didn't see Spotty. I searched for him ineach and every corner but in vain. And this time he had gone and would never come back. I cried and waitedfor him. But there were no signs of him and I only say him looking at me with his sparking eyes in my dream

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