题目

When we buy a house, we all want to have nice neighbours, because most of us think that it is helpful to live with some good neighbours. But what kind of neighbour is good? The answers are different from people to people. Here are my answers. First, it is very important to respect (尊重) each other. If our neighbour tries to know more about our life, what will we feel? He or she may also talk with others about our life. Do you want to live with him or her any more? The answer is “No”. We will feel very sad to have this kind of neighbour and move away quickly. Next, a good neighbo有一组数据3、5、7、a、4，如果它们的平均数是5，那么这组数据的方差是(    )A．2B．5C．6D．7