Question: when did hong kong go back to china
[{'answer': '30 June 1997', 'provenance': [{'wikipedia_id': '2093431', 'title': 'Handover of Hong Kong', 'start_paragraph_id': 9, 'start_character': 572, 'end_paragraph_id': 9, 'end_character': 584, 'bleu_score': 1.0, 'section': 'Section::::Overview.\n'}]}]