Explanation:

- Section 172 of the Indian Contract Act, 1872, deals with the concept of a pledge.

- Pledge: It involves the bailment of goods as security for payment of a debt or performance of a promise.

- Bailment: A broader term involving the delivery of goods from one person to another for a specific purpose, not necessarily for security.

- Finder: Refers to a person who finds goods that do not belong to them and involves obligations regarding those goods.

- Agency: A relationship where one person (the agent) is authorized to act on behalf of another (the principal).

- Pledge is the correct answer as it corresponds to the provision in Section 172.