Question: where does the energy to hydrolyze water come from
[{'answer': 'natural gas', 'provenance': [{'wikipedia_id': '3206764', 'title': 'Electrolysis of water', 'start_paragraph_id': 48, 'start_character': 138, 'end_paragraph_id': 48, 'end_character': 149, 'bleu_score': 1.0, 'section': 'Section::::Applications.\n'}]}]