According to the lesson, what brought about the need for social reform? a: too many new immigrants. b: rapid growth of large cities tooc: little cultural diversity d: industrial corruption

B. rapid growth of large cities.

Explanation:

During the Progressive Era of the United States, the country experienced very rapid growth of large cities. As industry developed, more and more factories and businesses were established in the cities, and people from rural areas moved to cities in order to look for work. Population also increased due to the high number of immigrants who arrived to the country. This rapid growth of cities led to social reform, as issues such as inequality and poverty required government intervention.