## **Core Concept**
The question pertains to the application of behavioural sciences in Preventive and Social Medicine (PSM), a crucial aspect of public health. Behavioural sciences help in understanding the behaviour of individuals and communities, which is essential in planning and implementing health programs.

## **Why the Correct Answer is Right**
The correct answer, **Health Belief Model**, is widely used in PSM. This model helps in understanding and predicting health behaviours by focusing on the attitudes and beliefs of individuals. It suggests that a person's health-related behaviour can be predicted by their perceptions of the threat posed by a health problem and the likelihood that taking action will reduce that threat. This model is extensively used in planning health education and promotion programs.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While *Learning Theory* does play a role in behavioural sciences, it is not as extensively used in PSM as the Health Belief Model. Learning Theory focuses on how behaviours are learned, but it doesn't directly address the specific health-related behaviours and beliefs.
- **Option B:** *Social Cognitive Theory* is indeed relevant, as it emphasizes the role of observational learning and social influences in behaviour. However, it is not as specifically tailored to health behaviours and beliefs as the Health Belief Model.
- **Option C:** This option seems to be missing, but based on the context, we can infer that other models or theories might not be as directly applicable or widely recognized in PSM as the Health Belief Model.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **Health Belief Model** includes several critical components: perceived susceptibility, perceived severity, perceived benefits, perceived barriers, self-efficacy, and cues to action. Understanding these components can help public health professionals design more effective interventions.

## **Correct Answer:** D. Health Belief Model.