Question: What is `before_action` (formerly known as `before_filter`)?

  1. A trigger that is executed before an alteration of an object's state
  2. A method that is executed before an ActiveRecord model is saved
  3. A callback that fires before an event is handled
  4. A method in a controller that is executed before the controller action method

Answer: The correct answer of the above question is Option D:A method in a controller that is executed before the controller action method