In which year did Ladakh become a Union Territory?

2019

The correct answer is Option (4) → 2019

This occurred on 31 October 2019, when the Jammu and Kashmir Reorganisation Act, 2019 came into effect. The Act bifurcated the former state of Jammu and Kashmir into two Union Territories: Jammu and Kashmir (with a legislature) and Ladakh (without a legislature). The bill was passed by the Indian Parliament in August 2019, following the abrogation of Article 370.