The correct answer is b. Laws were passed to ensure food and drug safety.
When Upton Sinclair wrote this book in the early 1900's, he was trying to bring attention to the fact that millions of immigrants living in urban areas were working at jobs that were extremely unsafe. This included descriptions of the disgusting work conditions that many immigrants faced in Chicago's meatpacking industry. Graphic details about the process in which companies made meat were outlined, but were not necessarily the focal point of the book.
However, the vivid descriptions caught the attention of millions of Americans who demanded changes to these unsanitary practices. This is when Teddy Roosevelt passed the Meat Inspection Act of 1906.