Question: who made up the labor force of the central pacific railroad while it was being built
[{'answer': 'Chinese emigrant workers'}, {'provenance': [{'wikipedia_id': '7734', 'title': 'Central Pacific Railroad', 'start_paragraph_id': 4, 'start_character': 423, 'end_paragraph_id': 4, 'end_character': 1164, 'bleu_score': 0.5375793762870611, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16199922857448890155}, 'section': 'Section::::Authorization and construction.\n'}]}]