Answer:
Observational study
Explanation:
The appropriate study for a gas station owner who wants to find out whether customers are satisfied with the service they receive or not is "Observational Study."
Given that the Observational study is a type of research study or scientific investigation in which the researcher observes the effect of an action or activities such as risk factors, or outcomes without a direct impact on the intervention from the researcher.
In this case, the satisfaction of customers concerning the services they receive can only be observed by the researcher without influencing the services or how the customers perceived their level of satisfaction.