The problem of international liquidity is related to the non-availability of

1. A

   goods and services

   Shortage of goods and services is a real-resource or supply problem, not what ‘international liquidity’ means in the exam sense. This option is not the key.

2. B

   gold and silver

   Gold and silver matter historically for reserves, but modern international liquidity is discussed mainly as hard-currency (especially dollar) availability. This option is therefore incomplete and not the key.

3. C

   dollars and other hard currencies

   International liquidity means the supply of reserve assets with which countries can settle external imbalances—chiefly US dollars and other hard currencies (and IMF-related assets). Non-availability of those is the liquidity problem. This option is the official key.

4. D

   exportable surplus

   Exportable surplus is a trade concept, not the definition of international liquidity. This option is not the key.

Summary. Official key is (c) dollars and other hard currencies. International liquidity is the stock of means of international payment. After Bretton Woods the dollar has been the core reserve currency; euros, yen and others count as hard currencies. Goods, bullion alone, or export surplus are different problems. Only (c) matches the term.