Question: when were genetically modified crops first introduced for commercial production in the u.s
[{'answer': '1994', 'provenance': [{'wikipedia_id': '216102', 'title': 'Genetically modified food', 'start_paragraph_id': 2, 'start_character': 55, 'end_paragraph_id': 2, 'end_character': 59, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '216102', 'title': 'Genetically modified food', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 466, 'bleu_score': 0.897547341647235, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 773017787150456162}, 'section': 'Section::::Abstract.'}]}]