**Core Concept**
Propaganda refers to the dissemination of information, ideas, or messages with the intention of influencing public opinion or behavior. It often involves the use of persuasive techniques to shape attitudes, beliefs, or actions. In the context of social and preventive medicine, propaganda can be used to promote health education, disease prevention, or public health initiatives.

**Why the Correct Answer is Right**
The correct answer, "Forcing of knowledge into mind," accurately describes the concept of propaganda. Propaganda involves the imposition of information or ideas onto individuals, often without their consent or critical evaluation. This can be done through various channels, such as mass media, advertising, or public relations campaigns. The goal of propaganda is to shape public opinion, attitudes, or behaviors, often by bypassing critical thinking or rational evaluation. In social and preventive medicine, propaganda can be used to promote health education, disease prevention, or public health initiatives, but it is essential to distinguish between propaganda and evidence-based information.

**Why Each Wrong Option is Incorrect**
**Option B:** "Active acquiring of knowledge" is incorrect because propaganda involves the imposition of information, not an active process of learning or acquisition. Acquiring knowledge actively implies a voluntary and engaged process, which is not characteristic of propaganda.

**Option C:** "Requiring knowledge after thinking" is incorrect because propaganda often seeks to bypass critical thinking or rational evaluation. Propaganda may present information in a way that is persuasive or convincing, but it does not require individuals to think critically or evaluate the information before accepting it.

**Option D:** "Training of people to use judgment before acting" is incorrect because propaganda often aims to influence behavior without necessarily promoting critical thinking or judgment. While some forms of health education may involve training individuals to use judgment, propaganda typically seeks to shape attitudes or behaviors through more subtle or coercive means.

**Clinical Pearl / High-Yield Fact**
A key distinction between propaganda and evidence-based information is the presence of critical evaluation or rational thinking. Propaganda often seeks to bypass critical thinking, whereas evidence-based information is grounded in scientific evidence and encourages individuals to evaluate information critically.

**✓ Correct Answer: A. Forcing of knowledge into mind**