What injustice did muckraker Lincoln Steffens uncover? unsafe tenements child labor political corruption trust agreements

Political corruption

Explanation:

The muckraker Lincoln Steffens was well-known for having exposed the corruption of municipal governments in various American cities. His articles were later published together in a book titled The Shame of the Cities. Steffens was a muckraker, which were journalists who wrote during the Progressive Era and focused on social problems such as corruption.

The correct answer is C, "political corruption."