Question: when did the sydney opera house became a world heritage site
[{'answer': '28 June 2007', 'provenance': [{'wikipedia_id': '28222', 'title': 'Sydney Opera House', 'start_paragraph_id': 5, 'start_character': 3, 'end_paragraph_id': 5, 'end_character': 15, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '28222', 'title': 'Sydney Opera House', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 372, 'bleu_score': 0.96746874041754, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11037516070106594767}, 'section': 'Section::::Abstract.'}]}]