Answer:
b. Participant observation
Explanation:
According to my research on different research methods, I can say that based on the information provided within the question this is an example of Participant Observation. This is a research method in which the researcher joins the subjects as part of the experiment in order to gain better insight on their experiences. Which is what Carmen is doing in this situation.
I hope this answered your question. If you have any more questions feel free to ask away at Brainly.