题目

请认真阅读下列短文，从短文后各题所给的四个选项(A、B、C和D)中，选出最佳选项，并在答题卡上将该项涂黑。 It was infour decades of nursing that I'd had such a terrible problem with a colleague.Rita seemed to look down upon me and I had no idea why. Every 1 I expressed had the opposite effect. Ourrelationship was so impossibly 2 that I didn't even pray about it. It is eightyears since I 3 from nursing, and certainly retired from everthinking about that 4 coworker. A pandemic (流行病) had 5 us all like a ton of bricks and even my townof Huntington had已知二次函数y=mx2+（m-3）x-3  （m＞0）（1）求证：它的图象与x轴必有两个不同的交点；（2）这条抛物线与x轴交于A（x1，0）和B（x2，0）（x1＜x2），与y轴交于点C，且AB=4，⊙M过A、B、C三点，求扇形MAC的面积S；（3）在（2）的条件下，抛物线上是否存在点P使△PBD（PD垂直于x轴，垂足为D）被直线BC分成面积比为1：2的两部分？若存在，请求出点P的坐标；若不存在，请说明理由．