Final answer:
Creating a multicultural literature department requires the most extensive modification of the curriculum, as it demands foundational changes in educational structure and resource allocation compared to other methods of incorporating diversity.
Step-by-step explanation:
Of the four ways identified to incorporate multicultural literature into the language arts program, establishing a multicultural literature department involves the most extensive modification of the curriculum itself. Unlike merely introducing diverse authors or embedding multicultural themes into existing courses, creating an entire department requires a foundational change in the educational structure. This includes a comprehensive curriculum, possibly new staff, and dedicated resources to support the diversity and inclusion goals. By comparison, creating a separate multicultural literature class, while significant, does not alter the curriculum to the same extent as it functions within the existing departmental framework.