Why Did the European Monetary Crisis of 2011 Occur

Why did the European monetary crisis of 2011 occur?

A) A handful of European countries borrowed heavily during an economic boom,and the global financial crisis of 2007 made it difficult to pay off those debts.
B) Greece,Ireland,Portugal,and Spain never fully adopted the euro,and their preference for a dual currency made investors wary.
C) Germany wanted to allow countries like Greece,Ireland,Portugal,and Spain to set their own monetary policies.
D) Countries heavily in debt wanted free monetary policy control so they could appreciate the currency in response to the crisis.