The correct option is C The signatories pledged to not make a separate armistice with the members of the Tripartite Pact.
On 1 January, representatives of major Allied powers met in Washington to discuss the way forward to end WWII. On 1 January 1942, the delegates from the US, UK, USSR, and China signed the document called the "Declaration of United Nations". The next day, 22 countries came forward to add their signatures to this document. The Allied powers pledged to cooperate to defeat the members of the Tripartite Pact (Germany, Italy, and Japan). The term "United Nations" was officially adopted in this conference.