The answer is C. middle-aged
"The increased population numbers between 1715 and 1789 demanded an increase in subsistence. Whether it was food grains or bread, the production could not keep up with the growing population. Wages for workers did not increase which meant the rich could afford subsistence but, the poor were left with nothing..."
The answer is "world-systems theory". World-systems theory is a multi-disciplinary, large-scale approach to world history and social change.
<em>Hope this helped! :)</em>