Suppose a Researcher Invites an Individual Participant to a Sleep

Multiple Choice

Suppose a researcher invites an individual participant to a sleep laboratory,but he refuses to fall asleep.Hours go by and the researcher cannot understand why the participant won't sleep.In the morning,a very tired participant asks if the real purpose of the study was to observe his reaction to having a rat in the bed with him.That the participant purposefully stayed awake thinking this was the nature of the study demonstrates

A) demand characteristics.
B) participant observation.
C) overt observation.
D) covert observation.