Final answer:
A written loan policy providing a discount to married couples is not a form of illegal discrimination.
Step-by-step explanation:
The correct option that is NOT a form of illegal discrimination is A. A written loan policy provides a 1/2% discount on loans to married couples. This policy does not discriminate based on any protected characteristic such as gender, race, ethnicity, or age. It simply provides a discount to married couples. Discrimination based on gender, race, ethnicity, or age would be present in the other options.