Which of the Following Did the National Research Council's Committee

Which of the following did the National Research Council's Committee on Research on Law Enforcement and the Administration of Justice identify as steps in designing policy experiments?

A) Choose an interesting problem-a policy question that people really care about or an existing procedure that clearly needs improvement.
B) Do some creative thinking to solve legal and ethical issues that may arise.
C) Rigorously maintain the random assignment of persons,cases,or other units into treatment and control groups throughout the experiment.
D) All of the above