If research participants given an inert substance that is presumed to have medicinal benefits experience pain relief,this illustrates

A) random assignment.
B) hindsight bias.
C) an illusory correlation.
D) the placebo effect.

Placebo Effect

A beneficial effect produced by a placebo drug or treatment, which cannot be attributed to the properties of the placebo itself, but to the patient's belief in it.

Inert Substance

A substance lacking active properties, particularly in the context of chemical reactions, not capable of inducing a change or reaction in other substances.

Pain Relief

Methods or treatments used to reduce or alleviate physical discomfort or pain.