Why Did European Countries Adopt the Euro

Why did European countries adopt the euro?

A) Adoption of the euro was connected to other favorable economic and political joint endeavors.
B) Most European currencies depended on the British pound,but Britain could no longer provide sufficient support for its own currency.
C) Germany could not continue to defend its currency when it reunified after the Cold War.
D) By adopting the euro,France would take Germany's place as the center of European monetary decision making.