In a randomized controlled experiment:

A. there is a control group and a treatment group

B. you control for the effect that random numbers are not truly randomly generated

C. you control for random answers

D. the control group receives treatment on even days only

Option A control group and a treatment group.

Explanation: the most important reasons for randomization in an experiment is to eliminate bias by reducing error. A control is usually used to see or show (baseline) if there is a significant in the treatment. A control group in an experiment is not manipulated or does not receive treatment while treatment group receives the manipulations. That is control in an experiment is not altered but treatment are altered to the aim of the experiment. The treatment group becomes good or better if only it's gives better results than the control group.