题目

阅读短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。 A long time ago, people thought that theSun went round the Earth. In some countries people even said that the Sun was agod (神). They thought the god drove across the sky each day on a goldenhorse. Now we know the Earth goes round the Sun. It takes the Earth a year togo all way round the Sun. Today men even know how far it is for the Earth to goround the Sun. They tell us that the Earth travels over a thousand miles a minuteon its journey round the Sun. The Sun is really a star. It is much biggerthan the Ear已知曲线C的方程为（2-t）x2+（3-t）y2=（2-t）（3-t），t＜3．（1）就t的不同取值讨论方程所表示的曲线C的形状；（2）若t=-1，过点P（4，0）且不垂直于x轴的直线l与曲线C相交于A，B两点．①求OA•OB的取值范围；②若B点关于x轴的对称点为E点，探索直线AE与x轴的相交点是否为定点．