Answer:
a) marketing plan
Step-by-step explanation:
Option B is incorrect because external people hardly know about the code of conduct of a company.
Option C is incorrect because if leadership team advertises about the ethical responsibility, people may think that the firm is not ethical.
Option D is wrong because culture and ethics are not the same thing.
Option E is false as the training materials do not define the term ethics and social responsibility.
Therefore, option A is correct because a marketing plan shows the ethical behavior and social responsibility towards people so that investors understand the commitment level of that company.