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);
case1: 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");