I would choose A and D. A under pins the code of ethics, D is often included to help users to better understand the code.
B: Terms of employment relate primarily to salary, hours, holidays etc.
C: Business values are primarily focused on the way the company wishes to conduct its affairs. For example, ‘Produce high quality products’, ‘Offer great value for money’. Corporate ethics are primarily concerned with issues of morality and integrity, eg ‘Treat employees fairly’. There is obviously an overlap for example ‘Treat customers with fairness’ can be both a corporate value leading to better profits and can be an ethical stance.