The best way to avoid demand characteristics is to __________.

A) tell participants which group (experimental or control) they are in when they arrive in the lab
B) make sure that only the experimenter knows which group participants are in
C) make sure that neither the experimenter nor the participant knows which group each participant is in
D) put all participants in the control group rather than the experimental group so that they are all treated the same

The best way to avoid demand characteristics is to make sure that neither the experimenter nor the participant knows which group each participant is in. This ensures that participants cannot guess the purpose of the study or behavior expected of them based on their group allocation, which would otherwise lead to demand characteristics. Option A is incorrect because telling participants which group they are in can lead to demand characteristics. Option B is not effective because the experimenter is still aware of group allocation which can inadvertently influence their behavior towards participants. Option D is also not a viable option because it does not allow for a comparison between groups which is fundamental for experimental research.