请阅读下面的程序 public class Demo { public static void sum(int a, int b) { System.out.println("int:" + (a + b)); } public static void sum(int a, float b) { System.out.println("float:" + (a + b)); } public static void sum(int a, double b) { System.out.println("double:" + (a + b)); } public static void main(String[] args) { int a = 10; long b = 20; sum(a, b); } } 下列选项中,哪一个是程序的运行结果( )
A. int:30
B. float:30.0
C. double:30.0
D. int:30.0