ProblemPart.GetString C# (CSharp) Method

    public virtual string GetString()
    {
        throw new Exception ("There is no way to represent this problem part as a string");
    }

 private void UpdateButtons()
 {
     //char[] letters = new char[]{'A', 'B', 'C', 'D', 'E'};
     for (int i = 0; i < answerButtonTexts.Length; i++)
     {         //set button text
         if (i >= availableAnswers.Count)
         {
             Debug.LogWarning("Not enough distractors");
             return;
         }
         ProblemPart part = (ProblemPart)availableAnswers[i];
         answerButtonTexts[i].text = part.GetString();             //"(" + letters[i] + ") " +
     }
 }