Compositions can be challenging.Logical formLearned from13 sentences. A world-city can be challenging.Logical formLearned from13 sentences. Change can be challenging.Logical formLearned from13 sentences. A path can be challenging.Logical formLearned from13 sentences. Poses can be challenging.Logical formLearned from13 sentences. A feature can be challenging.Logical formLearned from13 sentences. Cases can be challenging.Logical formLearned from13 sentences. A plan can be challenging.Logical formLearned from13 sentences. Characteristics can be challenging.Logical formLearned from13 sentences. A portion can be challenging.Logical formLearned from13 sentences. A teenager can be challenging.Logical formLearned from13 sentences. An act can be challenging.Logical formLearned from13 sentences. A (puzzle game) can be challenging.Logical formLearned from13 sentences. Artists can be challenging.Logical formLearned from13 sentences. An artist can be challenging.Logical formLearned from13 sentences.