单项选择题

有如下程序:
  #include"iostream.h"
  void main( )
  
   int x=1,a=0,b=0;
   switch(x)
    case 0:b++;
    case 1:a++;
    case 2:a++;b++;
   
  cout < < "a=" << a < < "," < < "b=" < < b;
  
 该程序的输出结果是

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