若有定义 : float x=1.5; int a=1,b=3,c=2; 则正确的 switch 语句是

A)

switch(x)

{ case 1.0: printf("*\n");

case 2.0: printf("**\n");}

B)

switch((int)x);

{ case 1: printf("*\n");

case 2: printf("**\n");}

C)

switch(a+b)

{ case 1: printf("*\n");

case 2+1: printf("**\n");}

D)

switch(a+b)

{ case 1: printf("*\n");

case c: printf("**\n");}