Upton Sinclair's The Jungle was published in 1906. His book details various problems in the meat packing industry. Historians and political scientists point to the publication of this book as an important event for free speech. What was the result of the publication of Sinclair's book?
A. Sinclair ran for public office on a business reform platform.
B. Sinclair was arrested for exposing business secrets.
C. Sinclair was prosecuted for criticizing business practices.
D. Sinclair created public pressure to change business regulations.