Question: who led the muslim forces that retook jerusalem
[{'answer': 'Abu Ubaidah', 'provenance': [{'wikipedia_id': '12537456', 'title': 'Siege of Jerusalem (636–637)', 'start_paragraph_id': 1, 'start_character': 199, 'end_paragraph_id': 1, 'end_character': 210, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '12537456', 'title': 'Siege of Jerusalem (636–637)', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 978, 'bleu_score': 0.972233322266093, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13495175610365994193}, 'section': 'Section::::Background.\n'}]}]