Step 1: Understanding the Concept:
- A Social Institution is an established and enduring pattern of social relationships and practices, organized to meet a specific social need. It comprises norms, roles, and values (e.g., the institution of family, the institution of education).
- A Social Group is a collection of two or more people who interact with one another and share a common identity.
Step 2: Detailed Explanation:
- (A) Family, (B) Marriage, and (C) Law are all major social institutions. They are complex systems of roles and norms that are deeply embedded in society to perform crucial functions (procreation, regulation of behavior, etc.).
- (D) A Peer group is a type of social group, typically a primary group, composed of individuals of similar age and social status. While it is an important agent of socialization, it is not a formal, society-wide institution like the others. It is a group, not an institutional system.
Step 3: Final Answer:
A Peer group is an example of a social group, not a social institution.