为什么答案是C啊??????

有以下程序

#include <stdio.h>

main()

{int a[]={2,3,5,4},i;

for(i=0;i<4;i++)

switch(i%2)

{case 0:switch(a[i]%2)

       {case 0:a[i]++;break;

        case 1:a[i]--;

       }break;

case 1:a[i]=0;

}

for(i=0;i<4;i++)  printf(“%d”,a[i]);  printf（”\n”）;

}程序运行后的输出结果是( C)

A)3 3 4 4    B) 2 0 5 0     C)3 0 40      C)0 3 0 4

i =0  

i%2 = 0 >>case 0  >>a[i]%2 = 0 >>case 0 a[i]++ >>a[0] = 3 

i =1  

i%2 = 1 >>case 1   a[1] =0;

i =2  

i%2 = 0 >>case 0  >>a[i]%2 = 1 >>case 1 a[i]-- >>a[2] =  4

i =3  

i%2 = 1>>case 1 >>a[3] =  0