The rhine river is found in:

north america
europe
africa
south america
asia

It is found in "EUROPE"

So, option B is your answer.

Hope this helps!

Air pollution: “combustion results in gases such as nitrogen oxides, nitrogen dioxide and particulates. the main causes of air pollution include transport, domestic combustion and industrial processes. pollutants from these sources can cause problems in the immediate vicinity and a distance away.”