Final answer:
The Hopi people ended up living with the Navajo primarily due to Spanish colonization, which led to wars, enslavement, and forced resettlements onto reservations.
Step-by-step explanation:
The event that caused some Hopi people to live with the Navajo was d) Spanish colonization. During the period of European expansion into the New World, indigenous groups such as the Hopi were significantly affected by the actions of European powers like Spain. The Spanish were the major European power in the Southwest, leading to wars and the enslavement of many native peoples. As a result of such colonization efforts and conflicts, some Hopi people were forced to reside on the same reservations as the Navajo after the Long Walk in 1864, where both groups faced the challenges of living with scarce resources.
Environmental changes, including drought and food scarcity, also prompted migrations and resettlements among indigenous people in the Southwest, particularly when traditional farming was no longer sustainable. While these factors did influence the movements and cultural shifts of various Native American groups, they were not the direct cause of the Hopi living with the Navajo, which was ultimately due to the pressures of Spanish colonization.