[Dev-C++] Array increment in C

Sorry it has been a while since I program. 
It is a stupid question. So, please forgive my ignorance. Maybe I lose my memory or something!!
I have a problem with the below code!!!
I can’t understand this part:     ++frequency [ responses [ answer ] ];
I know this part increment 1 to the value position of the result of this one responses [ answer ]
For example responses [ answer ]= 1; then    ++frequency [1]
But how did the result of frequency[ rating ]= 2,2,2,2,5,11,5,7,1,3 ?????
So can you please explain it to me?
//////////////////////////////////////////////////////
#include <stdio.h>
#define RESPONSE_SIZE 40
#define FREQUENCY_SIZE 11
int main()
{   
   int answer, rating, frequency[ FREQUENCY_SIZE ] = { 0 };
   int responses[ RESPONSE_SIZE ] = 
      { 1, 2, 6, 4, 8, 5, 9, 7, 8, 10,
        1, 6, 3, 8, 6, 10, 3, 8, 2, 7, 
        6, 5, 7, 6, 8, 6, 7, 5, 6, 6, 
        5, 6, 7, 5, 6, 4, 8, 6, 8, 10 };
   for ( answer = 0; answer <= RESPONSE_SIZE - 1; answer++ )
     ++frequency [ responses [ answer ] ];
   printf( "%s%17s\n", "Rating", "Frequency" );
   for ( rating = 1; rating <= FREQUENCY_SIZE - 1; rating++ )
      printf( "%6d%17d\n", rating, frequency[ rating ] );
   getchar();
   return 0;}
//////////////////////