Explanation:

- Section 4 of the Negotiable Instruments Act specifically defines a Promissory Note.

- A Promissory Note is a written and signed promise to pay a certain sum of money to a specific person or the bearer at a specified time or on demand.

- Cheques (Option 1) are covered under Section 6 of the Act, not Section 4.

- Hundis (Option 3) are traditional financial instruments not specifically defined in the Negotiable Instruments Act.

- A Bill of Exchange (Option 4) is defined under Section 5 of the Act, which is closely related to a Promissory Note but involves three parties.

- Option 5 mentions "Both 2 and 4," but Section 4 explicitly pertains only to Promissory Notes.

Correct Answer: Option 2 - Promissory Note