premise: Oscar has only visited Gambia, Rafael has only visited Bosnia & Herzegovinia, Brandon has only visited Mauritius, Walter has only visited Niger, Alan has only visited Papua New Guinea, Jaime has only visited Federated States of Micronesia, Alfredo has only visited South Africa, Brett has only visited Kazakhstan, Jim has only visited Norway, Cory has only visited Trinidad & Tobago
hypothesis: Frederick didn't visit Niger