单选题 有以下程序: #include <stdio.h> 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\n",a,b); }程序的运行结果是____