Question: what is the name of the river that forms the northern border of oregon
[{'answer': 'Columbia River', 'provenance': [{'wikipedia_id': '26811621', 'title': 'Oregon', 'start_paragraph_id': 1, 'start_character': 98, 'end_paragraph_id': 1, 'end_character': 112, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '26811621', 'title': 'Oregon', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 332, 'bleu_score': 0.5944478706134111, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17084264604437128742}, 'section': 'Section::::Abstract.'}]}]