若有定義:float w ; int a , b ; 則合法的switch語(yǔ)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 1+2:printf("**//n" ) ;}
D. switch(a+b ){case 1: printf("*//n" ) ;case 2:printf("**//n" ) ;default : printf("//n" ) ;}