Answer: A. A doctor who works in a small clinic
Explanation: During and after the Industrial Revolution, there was a certain stratification and appearance of the called middle class. Unlike unqualified and hard work in the factories, qualified work appeared and was sought with better wages. In addition, in urban areas there was a need for jobs such as managers, doctors, bankers, etc. Their status has improved over time and have become a middle class with incomes that they could afford even to employ a certain number of workers, buying decent homes, etc.