Final answer:
The detail that confirms the Wampanoag people's assistance to the Pilgrims is D, indicating how they taught the Pilgrims to live off the land after many suffered from starvation and disease.
Step-by-step explanation:
The detail that best supports the idea that the Wampanoag people taught the Pilgrims how to live off the land is option D: "After half of the Pilgrims died, the Wampanoag people taught them how to live off the land." This is directly related to the historical account of the Pilgrims' struggle during their first year at Plymouth colony. Their survival was largely due to the guidance and support of the local Native American tribes, notably the Wampanoag, who taught them essential agricultural techniques and helped them form treaties with neighboring tribes.
Details from the provided historical accounts recount that by early spring 1621, the relationship with the Wampanoag had improved, and with the help of members like Samoset and Squanto, the Pilgrims were taught how to cultivate crops, including maize, using local resources such as herring for fertilizer, which directly contributed to their subsistence and the success of the colony.