The correct answer is A. They were among the first to publicize immoral, corrupt practices of large industries.
Step-by-step explanation:
Upton Sinclair was a writer and journalist mainly known for his novel "The Jungle" that denounced the sanitary conditions in the industry, especially the conditions in the industry of slaughtering and distributing the meat of animals by the beginning of the 20th century. On the other hand, Ida Tarbell who was also a journalist during the Progressive Era wrote multiple articles and a book that focused on the Industry of Oil and criticized the corruption in this industry including tariffs and labor practices. Finally, Frank Norris who also lived during the Progressive Era and was a journalist focused on writing about the corruption of corporate monopolies (industries that won a specific service or product in an area) and the way these caused negative consequences on the general population.
This means, all of them (Upton Sinclair, Ida Tarbell, and Frank Norris) were journalists that focus on denouncing the negative aspects of different industries (meat industry, oil industry and monopolies) including the corruption and immoral practices in them, which was not common during this historical period. Thus, the best statement that describes these three journalists and writers is that "They were among the first to publicize immoral, corrupt practices of large industries".