challenge: According to Acemoglu, Johnson, and Robinson, what was a key factor in the rapid growth of banking and financial services in the United States in the 19th and early 20th century?
  
  A. The restriction of suffrage to a small group of elites
  B. The granting of monopoly rights to banks by the central government
  C. The presence of a dictator with centralized power
  D. The federal nature of the US political system, which led to competition among states to attract investment
  Answer: 