A (tooth peace symbol) can be hollow.Logical formLearned from3 sentences. Muscles can be hollow.Logical formLearned from3 sentences. A bump can be hollow.Logical formLearned from3 sentences. (Animal figures) can be hollow.Logical formLearned from3 sentences. Friendships can be hollow.Logical formLearned from3 sentences. Confines can be hollow.Logical formLearned from3 sentences. A gap can be hollow.Logical formLearned from3 sentences. Poundings can be hollow.Logical formLearned from3 sentences. A smile can be hollow.Logical formLearned from3 sentences. A snap can be hollow.Logical formLearned from3 sentences. A x3 can be hollow.Logical formLearned from3 sentences. A boy can be hollow.Logical formLearned from3 sentences. A world can be hollow.Logical formLearned from3 sentences. A voice may ring hollow.Logical formLearned from3 sentences. A cooker can be hollow.Logical formLearned from3 sentences.