A. Amazon
B. Nile
C. Indus
D. Danube

Submitted by: Salman bajwa

The Danube was once a long-standing frontier of the Roman Empire, and today flows through 10 countries, more than any other river in the world. The Danube river in Europe is the river that passes through the maximum number of countries in its journey.
It passes through 10 countries: Germany, Hungary, Romania, Austria, Serbia, Bulgaria, Croatia, Moldova, Ukraine, Slovakia.
It starts in Southern Germany and runs into the Black Sea through Romania.
It is the second-longest river in Europe after the Volga with a length of 2,850 kilometres.