Explanation:

- A formal sector establishment usually follows official labor laws and regulations. It often provides workers with benefits such as contracts and social security.

- An informal sector establishment typically does not adhere to formal labor laws. It often lacks formal contracts and benefits for workers.

- Option 1: Informal

- These establishments often employ fewer workers and operate with less formal arrangements.

- Workers usually don't have formal job security or benefits.

- Option 2: Formal

- Generally, larger establishments with formal procedures and recognition by the state.

- These follow labor regulations with formal hiring processes.

- Option 3: Both

- This refers to establishments that may have characteristics of both formal and informal sectors, though not commonly categorized this way.

- Option 4: None

- This suggests that neither an informal nor formal sector categorization fits, usually not applicable.

Given the description of having only four hired workers, such an establishment is likely smaller and less formal.

The correct answer is: Option 1: Informal