Historians believe it wasn’t the change in the weather that produced the first plentiful harvest for the Pilgrims in Plymouth colony, but rather it was their decision to allow people to hold that was responsible.

Private property

Explanation:

Realising the extinction of the entire community, the elders of the colony decided to try something radically different: the introduction of private property and the right of the individual families to keep the fruits of their own labor.

The Plymouth Colony experienced a great bounty of food. Private ownership meant that there was now a close link between work and reward. Industry became the order of the day as the men and women in each family went to the fields on their separate private farms. When the harvest time came, not only did many families produce enough for their own needs, but they had surpluses that they could freely exchange with their neighbors for mutual benefit and improvement.

letter d is correct.