Answer:
D. Conflict of interest
Step-by-step explanation:
According to the information about Mark, it is correct to say that the fact that he conducts research studies for two national car rental companies represents a potential conflict of interest.
This is a situation that occurs when the actions of a professional are configured as actions that put impartiality and ethics at risk, which is perceived by the fact that Mark conducts research studies for two competing companies, which may mean using information from one company for the other, or impartiality of its professional actions.