The imperialism had a massive effect on Europe, especially its western part. The countries that were imperial powers managed to get hold onto territories all over the world. By managing to control these territories, the imperialists had lot of natural resources and very cheap labor force at disposal. This enabled the industry in Europe to have constant growth, and the manufacturing to skyrocket, thus there were more and more products for the market, and more and more wealth was coming because of it, resulting in strong and well developed countries in Western Europe.
The correct answer is agriculture. It was made possible for people to live on a single piece of land and not be nomadic anymore in search of food. Agriculture enabled them to settle around river valleys like Nile or Tigris and Euphrates. This is the era when civilizations started rising worldwide.
The above system of United States Constitution is showing three organs of the state i.e Legislative branch, Executive branch and the Judicial branch.
And below each division, their works are given. Aswecan were that, each of the organ is at same height which shows that they are practicing equal powers and they don't interrupt in each others work.
They practice the system of <u>Checks</u><u> </u><u>and</u><u> </u><u>Balances</u> to ensure that none of the organ is enjoying and grabbing too much.
So, the most appropriate option is:

Checks and balances system.
And, we are done !!
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The countries the Britain conquered and we ruled those countries