Which of the following options best describes the modification required for the CreditCard class to allow a er to modify internal variables in a controlled manner? A) Create public setter methods within the CreditCard class to modify internal variables, ensuring validation checks within these methods to control the modifications. B) Expose internal variables directly, allowing ers to modify them without additional methods. C) Create private setter methods within the CreditCard class to modify internal variables, without any validation checks. D) Modify internal variables directly within the class methods without creating additional setter methods.