## **Core Concept**
The question pertains to the theory that explains the causation of disease due to social strain or stress. This concept falls under the category of psychosomatic medicine or psychoimmunology, where psychological factors influence the development and progression of diseases.

## **Why the Correct Answer is Right**
The correct answer, **C. Stress theory or General Adaptation Syndrome (GAS)**, proposes that social strain or stress can lead to disease. According to Hans Selye, the GAS theory explains how the body responds to stress, which can be caused by various factors including social strain. Chronic stress can lead to various health issues, including cardiovascular diseases, diabetes, and mental health disorders.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify a known theory related to disease causation by social strain.
- **Option B:** This option is incorrect as it does not directly relate to a recognized theory about social strain causing disease.
- **Option D:** This option is incorrect because it does not accurately represent a theory that links social strain directly to disease causation.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that chronic stress can significantly impact an individual's health, contributing to the development of various diseases. Understanding the impact of social strain and stress on health is crucial for providing holistic care to patients.

## **Correct Answer:** C. Stress theory or General Adaptation Syndrome (GAS).