The Vienna Convention on the Law of Treaties 1969 (VCLT) entered into force on:

1. The VCLT was adopted on 22 May 1969 and opened for signature on 23 May 1969. 2. Article 84(1) VCLT: 'The present Convention shall enter into force on the thirtieth day following the date of deposit of the thirty-fifth instrument of ratification or accession.' 3. The 35th ratification deposit was made on 27 December 1979 (Togo); the VCLT entered into force on 27 January 1980. 4. As of 2024, the VCLT has 116 States Parties. 5. India is NOT a party to the VCLT but follows much of its content as reflective of customary international law. 6. Hence option B is correct. _Source: UN Charter 1945 / Vienna Convention on Law of Treaties 1969 / ICJ Statute / ARSIWA 2001 — Vienna Convention on the Law of Treaties 1969, Article 84_