Final answer:
Upton Sinclair's book, The Jungle, embodied the belief of social justice in the Progressive Movement by exposing unjust and unsanitary practices in the meatpacking industry.
Step-by-step explanation:
Upton Sinclair's book The Jungle embodied the belief of social justice in the Progressive Movement. The novel exposed the unsanitary and exploitative practices in the meatpacking industry, highlighting the injustices faced by both consumers and workers. Through the publication of the book, Sinclair aimed to promote a Socialist ideology and inspire readers to challenge the capitalist system.