单选题 请说出E类中【代码1】~【代码3】的输出结果. class A { int m; int getM() { return m; } int seeM() { return m; } } class B extends A { int m ; int getM() { return m+100; } } public class E { public static void main(String args[]) { B b = new B(); b.m = 20; System.out.println(b.getM()); //【代码1】 A a = b; a.m = -100; System.out.println(a.getM()); //【代码2】 System.out.println(b.seeM()); //【代码3】 } }