以下程序运行结果是（ ）#include void f(int a, int b);void f(int a, int b){ int t; t = a; a = b; b = t;}void main(){ int x = 3, y = 2, z = 1; if (x > y) f(x, y); if (y > z) f(y, z); if (x > y) f(x, y); printf("%d, %d, %d", x, y, z);}
选项：

A:3, 2, 1;
B:1, 2, 3;
C:1, 3, 2;
D:2, 3, 1