In the last decade the largest number of refugees to the united states have come from all of the following countries except

The correct answer is Laos. 

It is difficult to predict why this is the case but it is. Although all four countries have their issues, fewest people came from Laos but it doesn't mean that it's the country with the smallest number of refugees, just that they were  accepted in the United States in the smallest amount compared to the remaining 3.