title: Return to same quiz for invalid option
body: <p>I am working on a multiple choice quiz. I want to be able to give user a chance to pick a valid option (a, b, or c) in case they chose a non-existent one (e.g. e). How do I get this done? At the moment, it goes right to the next quiz.</p>
  
  <p>Here's a portion of my code:</p>
  
  <pre><code>def ask_question(question,score):
      choices=('a','b','c')
      print(question[0])
      for multi in question[1:-1]:
          print("{0:&gt;5}{1}".format("",multi))
  while True: 
      answer = input("Please select an answer: ")
      if answer == question[-1] and answer in choices: 
          score += 1
  
      elif answer not in choices:
          print("Incorrect.Try again")
      break
  
  def main():
      questions = get_questions()
      score = 0
      number = 10
      print("Welcome to first quiz!")
      print()
  
      for next_question in range(number):
          question = random.choice(questions)
          score = ask_question(question, score)
          questions.remove(question)
      print("Your final score was {0} out of {1}.".format(score,number))
      if score &gt;= number * 0.75:
          print("You have passed.")
      else:
          print("You have failed.")
  if __name__ == "__main__":
      main()
  </code></pre>