Which of the following organisations is a classic example of an international cartel, where major producing countries coordinate to influence production and prices of a commodity?

Introduction / Context:
In economics, a cartel is an association of independent producers or organisations that agree to coordinate production, pricing or marketing to influence the market for a particular product. The most famous example on the global stage is an organisation of oil producing countries that coordinates crude oil output and thereby influences world oil prices. This question asks learners to identify that cartel from a list of major international bodies.

Given Data / Assumptions:
- A cartel coordinates output and sometimes prices among producers. - The options list OPEC, IMF, WTO and UNO. - One of these is an organisation of oil exporting countries. - The question expects the most widely cited example of an international cartel.

Concept / Approach:
OPEC stands for the Organization of the Petroleum Exporting Countries. It is a group of oil producing nations that coordinate petroleum policies to influence global oil markets. This coordination often involves agreements on output levels, which is characteristic of a cartel. IMF, the International Monetary Fund, deals with monetary cooperation. WTO, the World Trade Organization, governs trade rules. UNO, the United Nations Organization, is a broad international political organisation. None of these latter three function as cartels coordinating commodity production. Thus the approach is to match the definition of a cartel to OPEC.

Step-by-Step Solution:
Step 1: Recall that OPEC is made up of countries that are major exporters of crude oil. Step 2: Note that OPEC members meet to decide production quotas and sometimes influence global oil prices. Step 3: Recognise that this type of coordinated control over output and prices is the hallmark of a cartel in economics. Step 4: Consider the other options: IMF focuses on balance of payments, WTO on trade rules and UNO on peace and cooperation, none of which are commodity cartels. Step 5: Therefore, identify OPEC as the classic example of a cartel among the options.

Verification / Alternative check:
Economic textbooks and current affairs sources often introduce the concept of a cartel using OPEC as the primary real world example. They explain how OPEC decisions on production levels can cause oil prices to rise or fall, illustrating oligopoly and collusion concepts. In contrast, IMF, WTO and UNO are discussed in chapters on international institutions, not on cartels. Since so many sources consistently pair the idea of an international cartel with OPEC, this supports OPEC as the correct answer.

Why Other Options Are Wrong:
IMF: The International Monetary Fund lends to countries facing balance of payments difficulties and monitors macroeconomic stability; it does not coordinate production of goods and is not a cartel.
WTO: The World Trade Organization administers trade agreements and dispute settlement; it sets rules for trade but does not act as a group of producers fixing output or prices, so it is not a cartel.
UNO: The United Nations Organization is a global political and diplomatic forum that works for peace, development and human rights, and has no direct commodity cartel role.

Common Pitfalls:
Candidates sometimes confuse the roles of different international bodies and may think that any organisation with economic influence could be a cartel. For example, some may misinterpret WTO as a body controlling trade in a way similar to a cartel, or they may guess IMF due to its financial power. Another pitfall is ignoring the specific feature of a cartel, namely coordinated output decisions among producers. To avoid such errors, learners should strongly link the term cartel with OPEC and oil exporting countries in their memory, as this association is repeatedly used in both economics teaching and exam questions.

Final Answer:
The classic example of an international cartel among the listed organisations is OPEC, the Organization of the Petroleum Exporting Countries.