The exchange rate is the ratio at which the currency of one country is exchanged for the currency of another. Which method was developed by the World bank to exchange rates ?

The exchange rate is the ratio at which the currency of one country is exchanged for the currency of another. Which method was developed by the World bank to exchange rates ?

A. Breton Wood method
B. Free market exchange rate
C. Atlas method of exchange rate
D. Open market exchange rate