Which of the following statements about the UN Security Council is true?

The statement that the UN Security Council can impose sanctions and authorize military action is true because these are key functions of the Council as outlined in the UN Charter. The Security Council is responsible for maintaining international peace and security, and it has the authority to take various measures to address threats, including imposing economic sanctions and authorizing the use of force when necessary.

Sanctions can be used as a tool to compel states or groups to comply with international norms, while military action can be authorized in response to severe threats, such as acts of aggression or significant humanitarian crises. This mandate reflects the Security Council's role in addressing global conflicts and maintaining stability, which is a cornerstone of its existence within the United Nations system.

The other choices do not accurately reflect the structure or functions of the UN Security Council. It does include non-permanent members, thus eliminating the idea of it consisting only of permanent members. The notion that the Security Council is the most democratic body of the UN does not hold, as its decision-making process does not involve a one-member, one-vote system. Finally, not all decisions require a unanimous vote; instead, many decisions require a minimum of nine votes from the 15 members, which allows for more efficient decision-making in urgent situations.