Considering the cultural context of ancient Israel, what was the primary social and economic significance of gleaning, as exemplified in the story of Ruth?

A It was a form of charitable donation from wealthy landowners to support the Temple. B It was a legal mechanism to ensure fair distribution of land among all families. C It was a system of indentured servitude where the poor worked in the fields in exchange for food. D It was a safety net providing sustenance and social inclusion for the poor, widows, and foreigners, reflecting God's provision and compassion.