## Core Concept
The Declaration of Tokyo is a set of guidelines established by the World Medical Association (WMA) that focuses on the ethical principles for conducting medical research on human subjects. It was adopted in 1975 and has undergone several revisions. The core concept revolves around ensuring that medical research involving human subjects is conducted ethically.

## Why the Correct Answer is Right
The Declaration of Tokyo is specifically related to **medical research involving human subjects**. It provides guidelines to ensure that such research is conducted in an ethical manner, respecting the rights and welfare of the participants. This includes obtaining informed consent, ensuring that the research is scientifically justified, and minimizing risks to participants. The Declaration of Tokyo is a crucial document in the field of medical ethics, guiding researchers and clinicians on how to conduct studies involving human subjects ethically.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because the Declaration of Tokyo is not primarily related to animal welfare in research, which is covered by other guidelines such as the 3Rs (Replacement, Reduction, Refinement).
- **Option B:** This option is incorrect as the Declaration of Tokyo does not primarily focus on patient confidentiality in a broad sense but is more specifically concerned with ethical conduct in medical research.
- **Option C:** This option might seem plausible but is not accurate. While the Declaration of Tokyo does touch upon aspects relevant to clinical practice, its primary focus is on the ethical conduct of medical research.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the Declaration of Tokyo emphasizes the importance of **informed consent** from participants in medical research. Researchers must ensure that participants understand the purpose, risks, and benefits of the research and provide their consent freely.

## Correct Answer: D. Medical research involving human subjects.