Final answer:
The main economic reason for western imperialism was that European nations needed raw materials to fuel their industrialized economies.
Step-by-step explanation:
In the context of western imperialism, the main economic reason was b. European nations needed raw materials such as rubber, petroleum, and palm oil to fuel their industrialized economies. The industrialized nations sought to acquire colonies in order to gain control over lands that could provide them with these resources for their industries. These resources were essential for the growth and sustenance of their economies, allowing them to manufacture goods to be used domestically and exported to other markets.
This drive for raw materials was a fundamental component of the broader imperialist agenda. European nations established colonies to secure a reliable and cheap supply of resources, which would further their economic power and expansion. This economic motive, combined with other factors such as political, cultural, and military considerations, drove the era of western imperialism in the 19th century.