Rick Has High Blood Pressure and Decides to Try an Herbal

Rick has high blood pressure and decides to try an herbal supplement recommended by his friend.Which of the following questions would NOT have helped Rick scientifically evaluate his friend's recommendation before he began taking the herbal supplement?

A) Has this herbal supplement been studied in a clinical trial by trained medical professionals?
B) If this supplement was studied,who paid for the study?
C) If this supplement was studied,how many people were included as patients in the study?
D) Is this supplement all natural?