题目

They will move to a new apartment next month. It is _________ the one where they are living now. A. twice the size of   B. twice as bigger as  C. twice the size as   D. twice as bigger than 答案：A 解析: 略 一口袋中有4个红球，3个黑球，从中随机取球，取一个红球得2分，取一个黑球得1分． (1)今从中随机取4个球，求得分ξ的概率分布和期望． (2)今从中每次取一个球，看清颜色后放回后再摸下次，求连续4次的得分η的期望．