The Balkan Peninsula is separated from the rest of Europe by the river.

Answer: Option A

The Balkan Peninsula is separated from the rest of Europe by the river Danube. Balkans, the the countries occupying the part of SE Europe lying south of the Danube and Sava Rivers, forming a peninsula bounded by the Adriatic and Ionian Seas in the west, the Aegean and Black Seas in the east, and the Mediterranean in the south.