若a、b、c1、c2、x、y均为整型变量,正确的switch 语句是()
A.
switch (a+b); { case 1: y=a+b; break; case 0: y=a-b; break; }
B.
switch a { case c1: y=a-b; break; case c2: x=a*d; break; default: x=a+b; }
C.
switch (a*a+b*b) { case 3: case 1: y=a+b; break; case 3: y=b-a; break; }
D.
switch(a-b) { default: y=a*b; break; case 3: x=a+b; break; case 10: case 11: y=a-b; break; }