题目

阅读理解 Native to America, the cane toad (癞蛤蟆) was introduced to Northern Queensland 70 years ago to control sugarcane beetles (甘蔗害虫). The toads failed in that duty but spread across Queensland and into neighboring northern areas. Now it calmly invades(侵略) the stats of Western Australia and New South Wales ( NSW). NSW wildlife experts fear the amphibians － which have poisonous backs that kill hungry predators (食肉动物) 一will have a terrible effect on native animals. Those fears may be about to be realized. Australia's leading government research body, the Common19．若P（1，4）为抛物线C：y2=mx上一点，则P点到该抛物线的焦点F的距离为|PF|=5．