B. Other two don't make sense.
The correct answer is A
The objective of the League of Nations was to keep peace and many countries joined after WWI, but its main flaw was the lack of authority to enforce the decisions reached. It is significant to mention that for example the US was not part of the League of Nations.
<u>When the UN was built after WWII</u>, the Security Council was in fact the organ specifically created in order to address the flaws of the former League, and to be in charge of keeping international peace and security. Anyway, its activity was mostly paralized during the Cold War. After the dismantling of the URSS it has been operating and sending peacekeeping military missions all over the world.
The main functions of the Security Council are the following: the establishment of peacekeeping operation and of international sanctions, and the authorization of military interventions.
