Little Radha : C++

Radha

#include <iostream>
using namespace std;

/**
  * This clas deals with alphabets of 
  * english language.
  *
  * Please check another code I published 
  * on my profile for improved version.
  *
  * @author Shrikrishna Meena
  * @created 15 November 2016  
  */
class alphabets {
   string alphaBets;
   public: 
   alphabets(){
       int i = 0;
        for(char a='a';a<='z';a++){
           this->alphaBets[i] = a;
           i++;
        }
        this->alphaBets[i] = ' ';
      
   }
   
   /**
     * returns the list of alphabets 
     * as characters array
     */
   string getList(){
      return this->alphaBets;
   }
};

/**
  * This is baby girl Radha.
  * Not definitely an AI system.
  * But knows some words.
  *
  * @author Shrikrishna Meena
  * @created 15 November 2016  
  */
class Radha {

    //Neurons
    string welC, in, out, abc;
    int spread_sz = 15;
    int spread[15] = {0,13,3,26,18,15,17,4,0,3,26,11,14,21,4};
    
   public :
   
    //constructor
   Radha() {
       //intialing vars
        alphabets alphaBets;
        this->abc = alphaBets.getList();
        this->welC = "Me: Hi! How are you?";
        this->out = "Enjoy!";
   }
   
   
   /*
    * A method to tell Radh to start talking.
    */
   void talk(){
      //Printing welcome message
      cout << this->welC << endl;
      //Requesting user response
      this->ask();       
   }
   
   private :
   
   /*
    * EAR of the Radha
    * Metod that deals with user input
    */
   void ask(){
      //Waiting for message
      cin >> this->in;
      //Triggering the brain
      this->brain();
   }
   
   /*
    * A tiny BRAIN of the Radha
    */
   void brain(){
       //Preparing reply in brain
      //and speaking to user
      this->speak("You: " + this->in);
      this->speak("Me: " + this->out);
      //Appending a secret word in reply
      this->tellSecret();
   }
   
   /*
    * Lips of the Radha
    * that speaks
    */
   void speak(string msg){
       cout << msg << endl;
   }
   
   /*
    * Part of brain
    * Generates a secret message.
    */
   void tellSecret(){
      string secret;
      for(int i = 0; i < this->spread_sz; i++) {
          int idx = this->spread[i];
          secret += this->abc[idx];
      }
      
      this->speak(secret);
   }
};

int main() {
    Radha R;
    R.talk();
    return 0;
}