(Vocabulary words) can be difficult.Logical formLearned from9 sentences. A walking can be difficult.Logical formLearned from9 sentences. A social problem can be difficult.Logical formLearned from9 sentences. Configurations can be difficult.Logical formLearned from9 sentences. Examinations can be difficult.Logical formLearned from9 sentences. Nests can be difficult.Logical formLearned from9 sentences. An exploration can be difficult.Logical formLearned from9 sentences. A situation may prove difficult.Logical formLearned from9 sentences. Reforestation can be difficult.Logical formLearned from9 sentences. Responsibility can be difficult.Logical formLearned from9 sentences. Stains can be difficult.Logical formLearned from9 sentences. Plants can be difficult.Logical formLearned from9 sentences. Classrooms can be difficult.Logical formLearned from9 sentences. Hygiene can be difficult.Logical formLearned from9 sentences. Complainants can be difficult.Logical formLearned from9 sentences.