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.
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; }