以下程序输出结果是______。#include int main ( ){int x=1,y=0,a=0,b=0;switch(x){case 1:switch (y){case 0 :a++ ;break ;case 1 :b++ ;break ;}case 2:a++;b++;break;case 3:a++;b++;}printf("a=%d,b=%d",a,b);return 0;}

A. a=1,b=0
B. a=2,b=1
C. a=1,b=1
D. a=2,b=2