Answer: Fundemental attribution errors, The actor-observer bias, and the self-serving bias.
Explanation:
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.
They offered defensive positions and safety to the people. They were also where the Lord lived and where the lord was is where the money was. Thus trade and economic prosperity happened around the castle. Many trades were needed to support the lord and his castle. The lords army had to be equipped and fed. Thus markets and tradesmen were needed to support the lord and his castle.