Question: which type of triangle must have perpendicular lines
[{'answer': 'a right triangle', 'provenance': [{'wikipedia_id': '76944', 'title': 'Perpendicular', 'start_paragraph_id': 53, 'start_character': 12, 'end_paragraph_id': 53, 'end_character': 28, 'bleu_score': 1.0, 'section': 'Section::::In polygons.:Triangles.\n'}]}, {'provenance': [{'wikipedia_id': '76944', 'title': 'Perpendicular', 'start_paragraph_id': 53, 'start_character': 0, 'end_paragraph_id': 53, 'end_character': 60, 'bleu_score': 0.8242367502646051, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5363577247689356913}, 'section': 'Section::::In polygons.:Triangles.\n'}]}]