Question: what was the main motive of salt march
[{'answer': 'challenge to British authority', 'provenance': [{'wikipedia_id': '677641', 'title': 'Salt March', 'start_paragraph_id': 3, 'start_character': 1089, 'end_paragraph_id': 3, 'end_character': 1119, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '677641', 'title': 'Salt March', 'start_paragraph_id': 3, 'start_character': 1042, 'end_paragraph_id': 3, 'end_character': 1297, 'bleu_score': 0.8004807984901331, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8187662529854631568}, 'section': 'Section::::Abstract.'}]}]