Explanation:

- Option 1: Real exchange rate

- The real exchange rate shows how much of a foreign good or service can be exchanged for a domestic one, accounting for inflation. It is the key measure of a country's international competitiveness, as it reflects the actual purchasing power of currencies.

- Option 2: Nominal exchange rate

- This rate only shows how much one currency is worth relative to another but does not account for differences in price levels or inflation. It is less useful for measuring competitiveness.

- Option 3: Superfluous exchange rate

- This term is not used in economics and is irrelevant here.

- Option 4: None of the above

- Since option 1 is correct, this is not the right answer.