Respuesta :
I am pretty sure the answer is A, seeing as though you are recording them which would be observing and you would only be able to tell their mood if you observed them over time. B and D are obviously wrong. And I'm not sure about C so you decide using your intelligence if you agree or not. Hope I helped. :p
Answer: A.Placing different groups of people in different colored rooms and recording their mood
Step-by-step explanation:
An observational study is a study in which a researcher just records behavior in a particular manner without interfering with the behavior.
In this study, the researcher has no influence or control over the variables .
From the given options , only option A representing a situation which can be an example of observational study."Placing different groups of people in different colored rooms and recording their mood "
Here the researcher just recording the mood of people without any influence.