Answer:
c. The observers could make unobtrusive observations by hiding.
Step-by-step explanation:
Unobtrusive observation: In psychological research, the term unobtrusive observation is described as an observation that doesn't require the experimenter or the researcher to intrude or interfere in any of the research contexts.
Participant or direct observation needs the experimenter or the researcher to be physically present in the surrounding environment where the research is being conducted and therefore it leads the participant's to alter or change their behavior to look good in front of the experimenter or the researcher.
In the question above, the correct answer is "option c".