Answer:
B
Step-by-step explanation:
Geography is most likely the factor that provides the most significant influence on the long-standing and multiethnic diversity of Southeast Asia. The region's diverse geography, including mountains, coastlines, and islands, has historically made it difficult for any group or culture to dominate the entire area and has encouraged the development of distinct cultural and ethnic groups. Additionally, the region's location as a crossroads of trade and migration has also significantly shaped its diverse population.