以下程序的正确运行结果是( )。#include <stdio.h>void num(){extern int x,y;int a=15,b=10;x=a-b;y=a+b;int x,y;int main(){int a=7,b=5;x=a+b;y=a-b;num();printf(&quot;%d,%d\n&quot;,x,y);return(0);}A.12,2 B.不确定 C.5,25 D.1,12