Step 1: Define.
The Euro (EUR) is the common currency used by the Eurozone countries within the European Union.
Step 2: Clear the distractors.
It is neither a landmass (A), nor a country name (B), nor an island (D).
Step 3: Conclude.
\[
\boxed{\text{Euro is the currency of the EU/Eurozone (Option C).}}
\]