A clamshell can be rugged.Logical formLearned from18 sentences. A cliff can be rugged.Logical formLearned from18 sentences. A city can be rugged.Logical formLearned from18 sentences. Boots can be rugged.Logical formLearned from18 sentences. A left wing can be rugged.Logical formLearned from18 sentences. A half can be rugged.Logical formLearned from18 sentences. (Mountain roads) can be rugged.Logical formLearned from18 sentences. A (mountain path) can be rugged.Logical formLearned from18 sentences. A backdrop can be constituted-of-or-filled-with rugged mountains.Logical formLearned from18 sentences. Walls can be rugged.Logical formLearned from18 sentences. Andes can be rugged.Logical formLearned from18 sentences. Stretches can be rugged.Logical formLearned from18 sentences. A display can be rugged.Logical formLearned from18 sentences. A battle can be rugged.Logical formLearned from18 sentences. An outline can be rugged.Logical formLearned from17 sentences.