Question: when was doctor who first aired in america
[{'answer': '1972', 'provenance': [{'wikipedia_id': '804487', 'title': 'Doctor Who in Canada and the United States', 'start_paragraph_id': 7, 'start_character': 82, 'end_paragraph_id': 7, 'end_character': 86, 'bleu_score': 1.0, 'section': 'Section::::History.:The 1970s: "Doctor Who" sold to the United States.\n'}]}, {'provenance': [{'wikipedia_id': '804487', 'title': 'Doctor Who in Canada and the United States', 'start_paragraph_id': 7, 'start_character': 0, 'end_paragraph_id': 7, 'end_character': 509, 'bleu_score': 0.976327165973018, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15510900465011874015}, 'section': 'Section::::History.:The 1970s: "Doctor Who" sold to the United States.\n'}]}]