Choose the sentence with the correct preposition :

The correct answer is Option (2) → I sat beside him

Beside means next to, at the side of. The sentence tells where I sat: next to him.

Why the Other Options are Incorrect?

Option 1: I sat besides him — Incorrect. Besides means in addition to or apart from, not next to.
Example: Besides English, she speaks French.

Option 3: I sat at him — Incorrect. At marks a point or a target (look at, throw at). One does not sit "at" a person.
Example: The boy threw a stone at the mango.

Option 4: I sat to him — Incorrect. To shows movement towards or a receiver (go to, give to). It does not show position.
Example: She walked to the station.