Question

who decides which currency each country in the world uses?
the united nations
each individual country
the european union
the united states

Explanation:

Countries have sovereignty over their monetary systems, including deciding their currency. The UN, EU, or US don't dictate this for all countries. Each country independently decides its currency (e.g., a country can issue its own or adopt another like the euro, but adoption is still a country's choice).

Answer:

B. each individual country