Option 1 -> The Act was not enacted in 2018, as the reorganization process began later.
Option 2 -> The Jammu and Kashmir Reorganisation Act was enacted in 2019, following the abrogation of Article 370 and Article 35A.
Option 3 -> The Act was not enacted in 2020; it had already come into effect by October 31, 2019.
Option 4 -> The Act was not enacted in 2021, as the reorganization had been completed well before this year.
Hence, Option 2 (2019) -> The Jammu and Kashmir Reorganisation Act, 2019 was passed by the Parliament in August 2019 and came into effect on October 31, 2019, bifurcating the erstwhile state into two Union Territories: Jammu and Kashmir (with a legislature) and Ladakh (without a legislature) -> correct