Can you believe that in ____ a rich country there should be ____ many poor people? [ ]

A. such; such

B. such; so

C. so; so

D. so; such

有以下程序
fun(int x,int y)return(x+y);
main()
int a=1,b=2,c=3,sum;
sum=fun((a++,b++,a+b),c++);
printf("%d",sum);执行后的输出结果是______。
(A) 6
(B) 7
(C) 8
(D) 9