(A) ignorance
(B) assistance
(C) attack
(D) ** security
EXPLANATIONS BELOW
Concept note-1: -By establishing a bond of solidarity between Member States, the League is considered the first attempt to build a system of collective security. This principle relied on a simple idea: an aggressor against any Member State should be considered an aggressor against all the other Member States.
Concept note-2: -Cardinal Richelieu proposed a scheme for collective security in 1629, which was partially reflected in the 1648 Peace of Westphalia.
Concept note-3: -Collective Security stands for the creation of a universal or global preponderance of power involving all the nations for the maintenance of international peace and security. Under it all the nations are ready to defend international peace and security through collective military action against aggression.
Concept note-4: -The false hopes of the UN The principle of collective security was nevertheless adopted once more by the United Nations, established by the San Francisco Charter on 26 June 1945.