某牧场的10头牛因误食疯牛病毒污染的饲料被感染,已知疯牛病发病的概率为0.02. 发布时间:2017-05-05 17:27 │ 来源:www.tikuol.com 题型:选择题 问题: 某牧场的10头牛因误食疯牛病毒污染的饲料被感染,已知疯牛病发病的概率为0.02.若发病的牛数为ξ,则Dξ等于A.0.2B.0.196C.0.8D.0.812
题型:选择题 读下列对话,在横线上填上汤的价格。Waiter: Hello! What would you like for lunch?Jack: I'd like some rice and fish, please.Waiter: Your rice and fish.Jack: I'd 1ike some noodles and beef, please.Waiter: Your noodles and beef.Jack: Thank you.Waiter: Anything else?Jack: Some soup and vegetables, please.Waiter: Your soup and vegetables. Here's your bill.Jack: Oh... Forty yuan. __________ 查看答案
题型:选择题 将一定量的化学式为xFeSO4•y(NH4)2SO4.6H2O的晶体加入到过量的NaOH溶液中加热,得到NH30.85g(假如生成NH3的全部逸出),过滤、洗涤、灼烧,得到Fe2O3固体2.0g.则关于x、y关系正确的是( )A.x:y=1:1B.x:y=1:2C.x:y=1:4D.x:y=2: 查看答案