Under Article 11 VCLT, States consent to be bound by a treaty may be expressed by:

1. Article 11 VCLT: 'The consent of a State to be bound by a treaty may be expressed by signature, exchange of instruments constituting a treaty, ratification, acceptance, approval or accession, or by any other means if so agreed.' 2. Articles 12-15 detail each mode: signature, exchange of instruments, ratification/acceptance/approval, accession. 3. Article 18 obliges States not to defeat the OBJECT AND PURPOSE of a treaty prior to its entry into force after signature or pending ratification. 4. 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 11_