Answer:
Demand for rubber was another factor that promoted European imperialism in the late nineteenth century, however, it was not the single factor.
Explanation:
The main goal of European imperialism was to extract economic resources from the colonized nations. Some of these resources were: gold, silver, rubber, coal, agricultural products such as sugar cane, and so on, and the specific type of resources varied depending on the geographical region that was colonized.
As a result, demand for rubber was another drive for European imperialism, in the particular regions where it is obtained: the Amazon Basin and the Congo Basin.
This imperalism was stronger in the Congo Basin, simply because they countries that form the Amazon Basin were independent nations by then (Brazil, Colombia, etc), while the Congo Basin was dominated by the French and the Belgian empires, where the local populations were subjected to brutal treatment, especially by the latter.