Mostly, the Europeans dominated because their numbers or military technology and organization were superior.
Considering the alternatives, the only alternative that represents any sort of military power being evolved with it is:
d. They built infrastructure to keep military units traveling and intimidating the locals.
Also, the British and other countries did build many railroads in Africa.
Both factory workers and slaves had to work long hours, and working conditions weren’t as sanitary as they are today.
On August 3, 1492, Columbus set sail from Spain to find an all-water route to Asia. On October 12, more than two months later, Columbus landed on an island in the Bahamas that he called San Salvador; the natives called it Guanahani.
