有以下程序:void sum(int *a){ a[0]=a[1]; }main(){ int aa[10]={1,2,3,4,5,6,7,8,9,10}, i; for(i=2;i＞=0;i--) sum(&aa[i]); printf("%d\n", aa[0]);}执行后的输出结果是( )。

A．switch( {case 1.0: printf("*\n"); case 2.0: printf("**\n");}
B．switch((in; { case 1: printf("*\n"); case 2: printf("**\n");}
C．switch(a + { case 1: printf("*\n"); case 2+1: printf("**\n");}
D．switch(a+ { case 1: printf("*\n"); case c: printf("**\n");}

A．x=4
B．x=8
C．x=6
D．x=12