阅读下面的代码: class Person{ void say(){ System.out.println("hello"); } } class Example{ public static void main(String[] args){ Person p1 = new Person(); Person p2 = new Person(); p2.say(); p1.say(); p2=null; p2.say(); } } 下列选项中,哪个是程序的输出结果?() A. hello B. hello hello C. hello hello hello D. 抛出异常