单选题：若a,b,c1,c2,x,y均是整型变量，正确的switch语句是

若a,b,c1,c2,x,y均是整型变量，正确的switch语句是@[D](2)

A. ```
switch(a-b)
{ default: y=a*b; break;
case 3: case 4: x=a+b; break;
case 10: case 11: y=a-b; break;
}
```
B. ```
switch(a+b);
{ case 1: y=a+b; break;
case 0: y=a-b; break;
}
```
C. ```
switch(a*a+b*b)
{ case 3:
case 1: y=a+b; break;
case 3: y=b-a; break;
}
```
D. ```
switch a
{ case c1: y=a-b; break;
case c2: x=a*d; break;
default: x=a+b;
}
```



A.```
switch(a-b)
{ default: y=a*b; break;
case 3: case 4: x=a+b; break;
case 10: case 11: y=a-b; break;
}
```
B.```
switch(a+b);
{ case 1: y=a+b; break;
case 0: y=a-b; break;
}
```
C.```
switch(a*a+b*b)
{ case 3:
case 1: y=a+b; break;
case 3: y=b-a; break;
}
```
D.```
switch a
{ case c1: y=a-b; break;
case c2: x=a*d; break;
default: x=a+b;
}
```


答案：D