Answer is D) a legal requirement.
You probably know that some drugs, such as Tylenol, can be purchased without a prescription (over the counter), while others, such as Xanax, require the guidance and prescription of a medical practitioner. This is due to this amendment, passed in 1951 by two Congressmen who used to be pharmacists.
Before this law, you could get any drug without a prescription, at least under federal law.
