Central banks oversee national banking regulation

Steps:

• Identify the role of each option in the financial system.
• Recall that control means setting monetary policy and supervising banks.
• Compare options: central banks handle national oversight, while others focus on specific services.
• Confirm through standard economic knowledge that central banks dominate in most countries.

Why A is correct:

• Central banks, like the Federal Reserve or European Central Bank, are defined by law as the primary regulators of a country's banking system, issuing currency and enforcing financial stability.

Why the others are wrong:

• B: Commercial banks provide everyday services like loans but operate under central bank rules.
• C: Investment banks focus on securities and mergers, not broad system control.
• D: The World Bank aids global development but lacks authority over national banking systems.

Final answer: A