题目

There is not enough oil in the world now. As time goes by ,it becomes less and less ,so what are we going to do when it runs out? Perhaps we will go back to use horses ,carriages and bicycles .In the Second World War ,some people didn＇t use gas made from petroleum （石油）in their cars .They made gas from wood and plants instead . The cars didn＇t go fast ,but they ran ,so this was better than nothing. However, in the future, we can＇t cut down all our trees to make gas; we need our trees for other things, too.Besides different types of gas, we can also use electricity(电)to run our c下列说法正确的是         。（1）从匀速传递的产品生产流水线上，质检人员每20分钟从中抽取一件产品进行检测，这样的抽样方法为分层抽样；（2）两个随机变量相关性越强，相关系数的绝对值越接近1，若或时，则与的关系完全对应（即有函数关系），在散点图上各个散点均在一条直线上；（3）在残差图中，残差点分布的带状区域的宽度越狭窄，其模型拟合的精度越高；（4）对于回归直线方程，当每增加一个单位时，平均增加12个单位；（5）已知随机变量服从正态分布，若，则。