To study the effect of alcohol on reaction time, subjects were randomly selected and given three beers to consume. Their reaction time to a simple stimulus was measured before and after drinking the alcohol. Which of the following is a correct statement?

(A) This study was an observational study.

(B) Lack of blocking makes this a poorly designed study.

(C) The placebo effect is irrelevant in this type of study.

(D) This study was an experiment with no controls.

(E) This study was an experiment in which the subjects were used as their own controls