Drug that must be sold by retail only when a prescription by RMP is produced is scheduled under:

**Core Concept**
The question is inquiring about the regulation of pharmaceuticals, specifically the requirement for a prescription by a Registered Medical Practitioner (RMP) to purchase certain medications. This is related to the scheduling of drugs under the Narcotic Drugs and Psychotropic Substances (NDPS) Act.

**Why the Correct Answer is Right**
The correct answer is related to the scheduling of drugs under the NDPS Act. Schedule H drugs are those that can only be sold by retail on the production of a prescription by a Registered Medical Practitioner. This is because these drugs are considered to have a high potential for abuse or have significant side effects that require close medical supervision.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct schedule of drugs that require a prescription. Schedule H drugs are the correct answer.
**Option B:** This option is incorrect because it refers to Schedule X drugs, which are those that can only be used for research purposes and are not intended for human consumption.
**Option C:** This option is incorrect because it refers to Schedule Y drugs, which are those that are manufactured in small quantities for export purposes only.

**Clinical Pearl / High-Yield Fact**
It is essential for medical professionals to be aware of the scheduling of drugs under the NDPS Act to ensure that they are prescribing and dispensing medications safely and responsibly.

**Correct Answer: H. Schedule H drugs.**