Answer:
All of the choices are correct.
Explanation:
Placebo in clinical trials is an element of research that is more of a deceiving treatment given to the participants or a group of participants. It acts as a psychological effect on the participants who already know that the actual treatment will improve their health or condition etc. This means that it helps the researchers to adjust the psychological effects of receiving medical attention and is often refereed to as placebo control as it can control outside factors. Similarly, these outside factors are known as confounding factors hence a placebo also assists in controlling or avoiding confounding factors. Hence, All of the choices are correct.
