若a、b、c1、c2、x、y、均是整型变量,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 +b) { case 3: case 1:y =a +b;break; case 3:y =b -a,break; }
C.
switch a { case c1:y =a -b;break; case c2:x =a *b;break; default: x =a +b; }
D.
switch(a -b) { default:y =a *b;break; case 3:case 4:x=a +b;break; case 10:case 11:y =a -b;break; }