Which 19th-century situation reveals a flaw in Adam Smith's theory of how the "invisible hand of the market works?

C) Poor citizens in capitalist countries endured harsh working conditions.

Explanation:

Adam Smith's theory and unconditional support of capitalism was challenged when workers were underpaid and mistreated for centuries. The idea that a company can and should do what it needs to do to earn profits with no intervention (the free market) leads to very little supervision and money going into protecting and ensuring the success of its own workers. While the CEO of a company can live in luxury, in a totally free market, they'd have no obligation to make sure their workers are taken care of in any capacity.