Answer:
D. The need to increase the number of soldiers for European armies.
Step-by-step explanation:
Many countries within Europe were superpowers on the global scale and did not need to look for more soldiers. Additionally, when European countries needed new soldiers they came from within their own country.
On the other hand, Europe was a competitive continent, especially in economics. So, they used imperialism for their own gain. They also believed that their life was superior and thus that they had the right to take control of countries in other regions.