Question: when did the radio become popular in canada
[{'answer': '1921', 'provenance': [{'wikipedia_id': '46702089', 'title': 'History of broadcasting in Canada', 'start_paragraph_id': 1, 'start_character': 55, 'end_paragraph_id': 1, 'end_character': 59, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '46702089', 'title': 'History of broadcasting in Canada', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 158, 'bleu_score': 0.929712191543383, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2359096858505552490}, 'section': 'Section::::Abstract.'}]}]