The UN defines indigenous populations as:

The correct answer is Option (1) → Comprising the descendants of people who inhabited the present territory of a country at the time when people of a different culture or ethnic origin arrived there from other parts of the world and overcame them.

Option (1) Comprising the descendants of people who inhabited the present territory of a country at the time when people of a different culture or ethnic origin arrived there from other parts of the world and overcame them. — Correct. The UN defines indigenous populations as the descendants of peoples who inhabited the present territory of a country when persons of a different culture or ethnic origin arrived from other parts of the world and overcame them.

Option (2) People who have lived in a particular territory for the last 100 years. — Incorrect. The definition rests on who first inhabited the land before outsiders overcame them, not on 100 years of living there.

Option (3) At least three generations living in the same area. — Incorrect. The UN definition does not count generations; it rests on descent from the people who inhabited the land before others arrived and overcame them.

Option (4) At least two generations living in a particular territory for the last 100 years. — Incorrect. Neither generations nor a 100-year period appears in the definition; it rests on descent from the people who were there first.