## Core Concept
A nuclear family is a fundamental unit of social structure, typically consisting of a group of individuals related by blood, marriage, or adoption. The core members of a nuclear family are usually the parents and their dependent children. This concept is crucial in understanding sociology, psychology, and family dynamics.

## Why the Correct Answer is Right
The correct answer, **C. Father, mother, and children**, accurately represents the traditional definition of a nuclear family. This composition includes two parents (or a single parent in some cases) and one or more children living together in a household. This family structure is often considered the most basic and universal form of family organization across cultures.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not accurately represent a nuclear family. A nuclear family specifically refers to parents and their children, not a broader group like grandparents and children.
- **Option B:** This option is incorrect because it includes siblings and parents, making it more representative of an extended family or a family with additional generations, rather than a nuclear family.
- **Option D:** This option is incorrect because it mentions husband, wife, and grandchildren, which would represent a multigenerational or extended family rather than a nuclear family.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the nuclear family structure is often considered the basic unit for studying family dynamics and social interactions. Understanding this concept is essential in fields like psychology, sociology, and family medicine.

## Correct Answer: C. Father, mother, and children