Final answer:
Upton Sinclair's "The Jungle" highlighted food safety concerns in the meatpacking industry, leading to legislative reforms for consumer protection during the Progressive Era.
Step-by-step explanation:
Upton Sinclair's book, "The Jungle," addressed prominent social concerns during the Progressive Era. Its subject matter was particularly focused on food safety and the meatpacking industry. The novel revealed the appalling conditions and unsanitary practices within the meatpacking industry of the time. While Sinclair intended to promote Socialism and bring attention to the struggles of immigrant workers, the public was most shocked by the descriptions of how their food was being processed. This public reaction led to important legislative reforms such as the Federal Meat Inspection Act and the Pure Food and Drug Act of 1906, which significantly improved food safety and consumer protection.