Question: what material was used to build the roofs of houses in burzahom
[{'answer': 'birch', 'provenance': [{'wikipedia_id': '46268924', 'title': 'Burzahom archaeological site', 'start_paragraph_id': 5, 'start_character': 555, 'end_paragraph_id': 5, 'end_character': 560, 'bleu_score': 1.0, 'section': 'Section::::Location.\n'}]}, {'provenance': [{'wikipedia_id': '46268924', 'title': 'Burzahom archaeological site', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 809, 'bleu_score': 0.8140715018984901, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13926935843682668864}, 'section': 'Section::::Location.\n'}]}, {'provenance': [{'wikipedia_id': '46268924', 'title': 'Burzahom archaeological site', 'section': 'Section::::Location.\n', 'start_paragraph_id': 5, 'end_paragraph_id': 5, 'meta': {'evidence_span': ['In the Kashmiri language \'Burzahom\' means "birch", a tree species (that generally grows in the elevation range of in the Himalayas), which is found in the excavated housing area in the form of roofing material, and thus confirming the existence of the tree even in the pre-historic Neolithic times', 'birch', 'The Burzahom site is a prehistoric settlement in the village of the same name in the Srinagar District.']}}]}]