The Great Recession and Subsequent Eurozone Crisis Brought About Which

The Great Recession and subsequent Eurozone crisis brought about which reform within the European Union?

A) The creation of a European Central Bank
B) Linking the value of the euro to gold
C) Establishing a permanent fund that could be used in the future to bail out members when they face severe financial troubles
D) A commitment to establish a Banking Union to exercise supervisory control over European banks
E) Allowing the European Central Bank to purchase national bonds