Concept:The Great Trek refers to the mass migration of Dutch-speaking settlers (Voortrekkers) from the Cape Colony into the interior of South Africa.Explanation:The British takeover of the Cape made many Dutch settlers unhappy with British rule and policies.To escape this, groups of Voortrekkers moved inland in the 1830s and 1840s.As they moved, they established new settlements and republics in the interior.This led to the spread and expansion of white communities beyond the Cape Colony.Answer:D. the expansion of white communities in South Africa.