Why Would a Country Use Another Country's Currency Instead of Its

Why would a country use another country's currency instead of its own?

A) This is the first step when a larger country takes over a smaller country.
B) Smaller countries want to reduce the instability of their own currencies.
C) The International Monetary Fund (IMF) forces smaller countries to adopt the U.S.dollar when they have serious currency crises.
D) Larger countries force smaller countries to adopt their currencies in order to facilitate trade.
E) Larger countries want to reduce the possibility of a global currency crisis.