Teaching can be challenging.Logical formLearned from27 sentences. A (security situation) may remain challenging.Logical formLearned from27 sentences. A repertoire can be challenging.Logical formLearned from26 sentences. A section can be challenging.Logical formLearned from26 sentences. An element can be challenging.Logical formLearned from26 sentences. A component can be challenging.Logical formLearned from26 sentences. A weekend can be challenging.Logical formLearned from26 sentences. An obstacle can be challenging.Logical formLearned from26 sentences. Thoughts can be challenging.Logical formLearned from26 sentences. Studies can be challenging.Logical formLearned from26 sentences. A voyage can be challenging.Logical formLearned from26 sentences. A side can be challenging.Logical formLearned from26 sentences. A book can be challenging.Logical formLearned from26 sentences. A contest can be challenging.Logical formLearned from26 sentences. Sections can be challenging.Logical formLearned from26 sentences.