premise: Derek has only visited Ecuador, Oscar has only visited Burkina, Darrell has only visited Barbados, Gabriel has only visited Grenada, Nathan has only visited Costa Rica, Dustin has only visited Haiti, Douglas has only visited South Africa, Phillip has only visited Egypt, Arnold has only visited Vatican City, Earl has only visited Republic of the Congo, Billy has only visited Ireland, Cecil has only visited Guinea
hypothesis: Darrell didn't visit Barbados