Which of the Following Statistical Studies Is an Experimental Study

Multiple Choice

Which of the following statistical studies is an experimental study? ​

A) A researcher observes the effect of alcohol consumption on reaction time by administering various quantities of alcohol to randomly-selected subjects.
B) A study is conducted to see if exposure to increased carbon dioxide levels increases tomato yields.Tomato plants are selected at random and are then exposed to various doses of carbon dioxide.
C) Two random samples of senior adults are selected.The first group watches a 30-minute presentation on medicare fraud, while the other group does not watch the presentation.A survey is then administered to measure the level of confidence the subjects have in their health care providers.
D) All of these are experimental studies.
E) None of these are experimental studies.