Question: who proposed the double helix structure of dna
[{'answer': 'James D. Watson', 'provenance': [{'wikipedia_id': '922489', 'title': 'The Double Helix', 'start_paragraph_id': 1, 'start_character': 174, 'end_paragraph_id': 1, 'end_character': 189, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Francis Crick', 'provenance': [{'wikipedia_id': '922489', 'title': 'The Double Helix', 'start_paragraph_id': 1, 'start_character': 354, 'end_paragraph_id': 1, 'end_character': 367, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '922489', 'title': 'The Double Helix', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 367, 'bleu_score': 0.92860998190983, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3274177132776560729}, 'section': 'Section::::Abstract.'}]}]