若a和b均是整型变量，以下正确的switch语句是
A、A. switch (a/b) { case 1: case 3.2: y=a+b; break ; case 0: case 5: y=a-b; }
B、B. switch (a*a+b*b); {case 3: case 1: y=a+b; break ; case 0: y=b-a; break; }
C、C. switch a { default : x=a+b; case 10 : y=a-b;break; case 11 : y=a*d; break; }
D、D. switch(a+b) {case 10: x=a+b; break; case 11: y=a-b; break; }