Explanation:

- Oh no is an expression of sudden emotion or reaction.

- It doesn't fit into grammatical structures like nouns or verbs.

- Often used to express surprise, dismay, or enthusiasm.

- Positioned in a sentence to convey emotions or sentiments.

- Options explained:

1. Preposition: Shows relation between words (e.g., in, on).

2. Article: Specifies nouns (e.g., a, an, the).

3. Noun: Represents a person, place, thing, or idea.

4. Interjection: Highlights emotions without grammatical connection.

- Correct option is option: 4 - Interjection.