Final answer:
Important decisions typically require a two-thirds majority, reflecting the need for broad consensus on significant issues like peace and security, and the admission of new members.
Step-by-step explanation:
Decisions on important questions, such as those on peace and security, admission of new members, and budgetary matters, often require a two-thirds majority. This type of supermajority is necessary to ensure a wide consensus on significant matters. For example, constitutional amendments often necessitate a supermajority to pass, which can range from a three-fifths to three-quarters majority. In the context of ratifying an amendment before it becomes law, three-fourths of the states must agree. Therefore, when answering the question provided, the correct choice is C) two-thirds majority.