题目

下面是一个2×2的列联表  y1y2总计 x1a2173 x222527 合计54b100 则表中a、b的值依次为( ) A．44,54                                                       B．52,46  C．54,46                                                       D．52,54 答案：BJesse is a high school student from a mountain village. For this reason or that, every evening he has to go home which is quite a few miles from his school, which takes him almost an hour or so. Therefore he is in great need of a proper bike so that he can save much time. ________57.Emily has decided to buy her lovely nephew, whose birthday is drawing near, a bike which owns comfortable seat safe handles and other special designs so that the little one can add fun to riding. ________58.Edwin would like to buy a bike in order that he can learn to ride on it for fun. He expects the bike will provide him with comfortable equipment and freestyle riding. ________59.Flora is eager to get a bike which is specially designed for girls and has bright and pleasant color. As she is a bit timid (胆小), she hopes that the bike will have enough safety equipment. ________60.Desmond has been promised to own a bike of his own! He is happy and thinks that his bike must own changeable speeds—great speed and normal speed.