Who is associated with exposing the poor conditions of the meatpacking industry?

Upton Sinclair is well-known for his expose of the poor and unsanitary conditions in the meatpacking industry, particularly through his novel "The Jungle," published in 1906. Sinclair aimed to draw attention to the exploitation of workers and the horrific conditions in which they labored. However, the shocking revelations about the meatpacking process and the lack of food safety regulations resonated with the public even more, ultimately leading to significant reforms, including the Meat Inspection Act and the Pure Food and Drug Act.

While other figures, such as Jane Addams and Ida Tarbell, were also influential in advocating for social reform and corporate accountability, their greatest impacts were in different areas. Jane Addams focused on social reform and women's rights through her work in settlement houses, while Ida Tarbell is known for her investigative journalism that targeted monopolies and corporate corruption, particularly concerning Standard Oil.

Theodore Roosevelt was a key figure in the implementation of Progressive Era reforms and supported regulatory measures in response to public outcry over conditions in industries like meatpacking. However, his association is more with the enforcement of reforms rather than the initial exposure of the conditions, which Sinclair highlighted in his literary work. Thus, Upton Sinclair is the correct answer for specifically exposing the issues within