若有定义:float w; int a,b;则合法的switch语句是( )
A.
switch(w) { case 1.0: printf(“*\n”); case 2.0: printf(“**n”); }
B.
switch(a) ; {case 1 printf(“*\n”); case 2 printf(“**n”); }
C.
switch(b) {case 1: printf(“*\n”); default: printf(“\n”); case 2,3: printf(“**n”); }
D.
switch(a+b) { case 1: printf(“*\n”); case 2: printf(“**n”); default: printf(“\n”); }