public class Test {public static int f(int n) {if (n == 1)return 1;elsereturn f(n - 1) + 1;}public static void main(String[] args) {int i, j = 0;for (i = 1; i <= 3; i++)j += f(i);System.out.println(j);}}以上程序的执行结果是？

A. 1
B. 3
C. 6
D. 0