Answer:
Naturalistic Observation
Explanation:
According to my research on the different types of research methodology, I can say that based on the information provided within the question the research method best represented in this situation is called a Naturalistic Observation. This is a study approach in which the researcher observes a subject in it's natural environment without interference from the researcher or any 3rd party that might affect the results. Which is what Dr. Martinez is using to determine what the children prefer.
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