Which of the following was an important element in the growth of political machines

Political machine, in U.S. politics, a party organization, headed by a single boss or small autocratic group, that commands enough votes to maintain political and administrative control of a city, county, or state.

The rapid growth of American cities in the 19th century, a result of both immigration and migration from rural areas, created huge problems for city governments, which were often poorly structured and unable to provide services. In those conditions, political machines—such as Tammany Hall, run by boss William Magear Tweed (1823–73) in New York City—were able to build a loyal voter following, especially among immigrant groups, by performing such favours as providing jobs or housing.