Explanation

Afghans is correct because OCHA reported a large number of Afghan displacements in 2019. Syrians are incorrect because the question asks about the specific group cited by OCHA for that year's figure. Yemenis are incorrect because this option does not match the data point provided by OCHA for 2019. Turks are incorrect because they were not the primary group cited with that displacement number in the context of the question.