What is the double coincidence of wants, and why does it hinder barter?

What is the double coincidence of wants, and why does it hinder barter?

• A. It occurs when both traders want exactly the same good, making trades straightforward.
• B. It occurs when each trader must want the other's offer at the same time, making exchanges rare and costly.
• C. It refers to the need for a single currency to exist for trade.
• D. It happens when money is absent and trades are only possible with barter.

Answer: (B)