Dr. B is doing a study to assess whether those who do and do not receive snacks at a presentation differ in their rating of how good the presentation was. Therefore, Dr. B is interested in understanding a cause-effect relationship. To do so, he randomly assigns participants to either receive snacks or no snacks. After the presentation he has individuals complete a survey wherein they rate the presentation. Which of the following is true if his study is useful in determining cause-effect?

Group of answer choices

a) you cannot tell what kind of design he would need for this

b) he can use an experimental or non-experimental design

c) all study designs can tell us the same thing so it doesn't matter which kind he uses

d) it must be an experimental design