Correct Answer: Chinese yuan

Solution : The correct answer is d) Chinese yuan

The Chinese yuan is an example of a non-convertible currency. A non-convertible currency refers to a currency that is not freely traded or exchanged on the international foreign exchange market. It means that there are restrictions or limitations on the convertibility of the currency into other currencies or its use in international transactions.

While the US dollar (a), Euro (b), and Swiss franc (c) are freely convertible currencies, widely accepted and traded in international markets, the Chinese yuan has historically had restrictions on its convertibility. However, it's important to note that currency policies and convertibility restrictions can change over time, and the status of a currency as convertible or non-convertible may be subject to updates and developments in currency regulations and international agreements.