若a和b均是正整数型变量,以下正确的switch语句是( )。
A.
switch ( pow(a,2)+pow(b,2)) { case 1: case 3: y=a+b; break; case 0: case 5: y=a-b; }
B.
switch (a*a+b*b) { case 3: case 1: y=a+b; break; case 0: y=b-a; break; }
C.
switch a { default : x=a+b; case 10 : y=a-b;break; case 11 : y=a*d; break; }
D.
switch(a+b); { case 10: x=a+b; break; case 11: y=a-b; break; }