Please tell me which one is the correct answer

14. Mr. H is the manager of Human Resource Department in a big company. He is instructed by the CEO to write an Employee Ethical Codes to regulate employees' ethical behavior. As an experienced HR manager, he knows that the Employee Ethical Codes may NOT work as expected because of which of the following problems? * a. Ethical codes are hard to be enforced in forms b. Top level leaders are not involved in the program c. The Ethical Codes do not motivate employees to follow rules. O d. All of the above