Question: when did the construction of the cpr begin
[{'answer': '1881', 'provenance': [{'wikipedia_id': '5959', 'title': 'Canadian Pacific Railway', 'start_paragraph_id': 1, 'start_character': 183, 'end_paragraph_id': 1, 'end_character': 187, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '5959', 'title': 'Canadian Pacific Railway', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 1156, 'bleu_score': 0.9769311161719021, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3836282814341316151}, 'section': 'Section::::Abstract.'}]}]