Question: where did the central pacific begin building the transcontinental railroad
[{'answer': 'Omaha , Nebraska', 'provenance': [{'wikipedia_id': '36541', 'title': 'First Transcontinental Railroad', 'start_paragraph_id': 123, 'start_character': 37, 'end_paragraph_id': 123, 'end_character': 53, 'bleu_score': 1.0, 'section': 'Section::::Construction.:Union Pacific construction.\n'}]}, {'provenance': [{'wikipedia_id': '36541', 'title': 'First Transcontinental Railroad', 'start_paragraph_id': 57, 'start_character': 0, 'end_paragraph_id': 57, 'end_character': 598, 'bleu_score': 0.9796927878356411, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6089189192937534088}, 'section': 'Section::::Transcontinental route.:Construction begun.\n'}]}]