Answer:
The answer to the question: By building military bases around the world, imperialist nations mainly aimed to:____, would be: Resupply their naval vessels so that military presence, and power, could be retained and the empires could reach their colonies and maintain control of them, at all times.
Explanation:
This tactic from imperialist nations, especially countries like Britain, was what allowed them to almost constantly retain control of their colonies, as far out as the Southeast Asian nations, without having much opposition. Naval power, and military presence, became one of Britain´s best sources to maintain their empire for such a long time. By establishing several military, and naval, bases around the world, the British Navy was able to supply their ships, but also the military forces that were left behind to ensure the safety of their colonies. This is why the answer given above is the correct one.