Question

what was a key reason for the expansion of the middle class in growing american cities?
factories started paying higher wages than office jobs.
white - collar jobs often paid better than factory jobs.
rural workers were forced to come and work in cities.
increase in factory jobs contributed to increase in white - collar jobs.

Explanation:

The growth of factory jobs led to a need for administrative, managerial and other white - collar support roles. These white - collar jobs contributed to the expansion of the middle class as they often came with better pay and working conditions compared to blue - collar factory jobs.

Answer:

D. Increase in factory jobs contributed to increase in white - collar jobs.