题干

对于一个容量为N的总体抽取容量为n的样本,当选取简单随机抽样、系统抽样和分层抽样三种不同的方法抽取样本时,总体中每个个体被抽中的概率分别为P1,P2,P3,则(  )

A:P1=P2=P3

B:P1=P2<P3

C:P2=P3<P1

D:P1=P3<P2

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A

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    I set out to change the lives of those who need help by joining my school's newly formed Free The Children Club. Through the determination of friends, the group has grown bigger and stronger each year. Over the past two years my friend, Alex Auclair, and I have become the leaders of the club.

    Already, after only two years of fundraising, we have accumulated over three thousand dollars and almost two thousand food items through various fundraising efforts. For example, each year a 24-hour famine (饥饿) is planned resulting in absolutely no consumption (消耗) of food. By taking part in these activities, we put ourselves in the shoes of someone living in poverty.

      No money raised goes to waste. At the end of each school year, the group takes a vote to determine where our funds will be spent and donated. Last year, we bought enough desks, chairs, supplies and textbooks for every student in a Kenyan school. This year, we plan to spend our earning helping out families in Sierra Leone.

    Poverty is a worldwide issue affecting the lives of people in not only developing countries, but also first-world countries such as Canada, the United Kingdom and Japan. Living in poverty can result in hunger, many forms of disease, lack of education, and for millions, death. It does not have to be this way. You too can form a club like the Free The Children Club or you can participate in events outside of school. Get your friends, family, even your community involved in fundraising. Do what you can to change the world.