The Rhine river of northern Europe empties into

the Baltic sea
the North sea
the Bay of Biscay
the Adriatic sea

The correct answer is: B. the North Sea

The Rhine is the longest river in both Germany and Western Europe. It flows through Germany, France, Switzerland, Liechtenstein, and the Netherlands, and empties into the North Sea.

The Baltic Sea is an inland sea located in Northern Europe. It is bounded by Sweden, Finland, Estonia, Latvia, Lithuania, Poland, Germany, Denmark, and Russia.

The Bay of Biscay is an inlet of the Atlantic Ocean located on the western coast of France and the northern coast of Spain.

The Adriatic Sea is an extension of the Mediterranean Sea located between Italy and the Balkan Peninsula.