A distinction can be challenging.Logical formLearned from4 sentences. An outcome can be challenging.Logical formLearned from4 sentences. Objects can be challenging.Logical formLearned from4 sentences. (Graduate programs) can be challenging.Logical formLearned from4 sentences. (I spy riddles) can be challenging.Logical formLearned from4 sentences. A (research issue) can be challenging.Logical formLearned from4 sentences. Mathematics can be challenging.Logical formLearned from4 sentences. An outbreak can be challenging.Logical formLearned from4 sentences. Some cases can be challenging.Logical formLearned from4 sentences. Alternatives can be challenging.Logical formLearned from4 sentences. Benchmarks can be challenging.Logical formLearned from4 sentences. A variation can be challenging.Logical formLearned from4 sentences. Rivals can be challenging.Logical formLearned from4 sentences. Detection can be challenging.Logical formLearned from4 sentences. An assessment can be challenging.Logical formLearned from4 sentences.