Final answer:
The Alps represent an example of a physical trade barrier in Europe due to their challenging terrain and size, making travel and trade more difficult between regions separated by this mountain range.
Therefore, option C is correct.
Step-by-step explanation:
An example of a physical trade barrier in Europe is C. the Alps. While rivers such as the Rhine and the Danube have historically been avenues for trade and transport through Europe, facilitating the exchange of goods and cultural connections, mountain ranges such as the Alps can serve as formidable barriers, impeding travel and trade between regions. The Alps have presented challenges for trade and communication due to their sheer size and difficult terrain, often necessitating the construction of tunnels, roads, and railways to connect countries separated by these mountains.
The Alps act as a natural border and also contribute economically, as they host important industries like tourism and have influenced the culture and lifestyle throughout history. However, in terms of physical barriers to trade and movement, their imposing presence has made them a significant obstacle to overcome for the flow of goods between nations.