Question: when did construction of the transcontinental railroad begin
[{'answer': 'January 8 , 1863', 'provenance': [{'wikipedia_id': '36541', 'title': 'First Transcontinental Railroad', 'start_paragraph_id': 116, 'start_character': 3, 'end_paragraph_id': 116, 'end_character': 19, 'bleu_score': 1.0, 'section': 'Section::::Construction.:Central Pacific construction.\n'}]}, {'provenance': [{'wikipedia_id': '36541', 'title': 'First Transcontinental Railroad', 'start_paragraph_id': 56, 'start_character': 0, 'end_paragraph_id': 56, 'end_character': 1181, 'bleu_score': 0.8902581227308141, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8909702416253882748}, 'section': 'Section::::Transcontinental route.:Construction begun.\n'}]}]