Final answer:
The best-reflected principle of democracy in the context of the Industrial Revolution is Social mobility, as the text discusses socialist responses to economic inequality.
Step-by-step explanation:
The principle of democracy that is best reflected in the paragraph about the Industrial Revolution would be C. Social mobility. This concept is highlighted by the various avenues that political philosophers during the Industrial Revolution proposed to address the issues of poverty and economic inequality, including the social ownership of means of production. Many of these thinkers were labeled as socialists for their innovative, though at times radical, ideas to improve social and economic conditions for the poor and working classes, implying a shift towards greater social mobility.