Which river flows through cities such as Bonn and Cologne?

The Rhine River is the correct answer because it is one of the major rivers of Europe, flowing through several significant cities in Germany, including Bonn and Cologne. This river originates in the Swiss Alps and travels northward through Germany and the Netherlands before emptying into the North Sea. The Rhine is known for its important role in trade, transportation, and cultural significance in the region.

The other rivers mentioned, while well-known, do not flow through Bonn and Cologne. The Seine flows through Paris, the Thames runs through London, and the Loire is located mainly in central and western France. This geographical context reinforces the predominance of the Rhine in relation to the cities specified in the question.