Explanation:

- Herbert Hyman

- He is credited with defining and popularizing the concept of "political socialization."

- Pioneer in studying how individuals form political beliefs through various influences.

- Herbert Spencer

- Known for contributions to social Darwinism and philosophy.

- Did not specifically focus on political socialization.

- Almond Powell

- Refers to Gabriel Almond and Bingham Powell, who collaborated on comparative politics.

- Did not coin or extensively focus on the primary concept of political socialization.

- Easton and Dannis

- David Easton is known for political system theory.

- Not primarily associated with introducing the term "political socialization."

Correct Answer: Herbert Hyman