A heel can be hollow.Logical formLearned from4 sentences. ....s can be hollow.Logical formLearned from4 sentences. A (gut cavity) can be hollow.Logical formLearned from4 sentences. Components can be hollow.Logical formLearned from4 sentences. Bread can be hollow.Logical formLearned from4 sentences. Structures can be hollow.Logical formLearned from4 sentences. A virus can be hollow.Logical formLearned from4 sentences. A reward can be hollow.Logical formLearned from4 sentences. Gates can be hollow.Logical formLearned from4 sentences. A sack can be hollow.Logical formLearned from4 sentences. Hemispheres can be hollow.Logical formLearned from4 sentences. (Carbon nanotubes) can be hollow.Logical formLearned from4 sentences. Spicules can be hollow.Logical formLearned from4 sentences. Rollers can be hollow.Logical formLearned from4 sentences. A dielectric can be hollow.Logical formLearned from4 sentences.