Which of the following is or are true of a placebo?

A) Placebos are used in randomized clinical trials.
B) Placebos contain the currently most effective treatment for a condition.
C) Participants who receive a placebo during a trial know that they are receiving a placebo.
D) all of these choices

Randomized Clinical Trials

A study design that randomly assigns participants into experimental or control groups to test the efficacy or effectiveness of therapies or interventions.

Placebo

An inert or non-active substance given to a patient in place of a medication, used in clinical trials to test the efficacy of treatments.