若有定义:floatx=1.5;inta=1,b=3,c=2;则正确的switch语句是()

A. switch(x){case1.0:printf("*\n");case2.0:printf("**\n");}
B. switch((int)x);{case1:printf("*\n");case2+x:printf("**\n");}
C. switch(a+b){case1:printf("*\n");case2+1:printf("**\n");}
D. switch(a+b){case1:printf("*\n");casec:printf("**\n");}