Question: what is the difference between air brakes and hydraulic brakes
[{'answer': 'Hydraulic brakes use a liquid', 'provenance': [{'wikipedia_id': '6889398', 'title': 'Air brake (road vehicle)', 'start_paragraph_id': 11, 'start_character': 114, 'end_paragraph_id': 11, 'end_character': 143, 'bleu_score': 1.0, 'section': 'Section::::Advantages.\n'}]}, {'provenance': [{'wikipedia_id': '6889398', 'title': 'Air brake (road vehicle)', 'start_paragraph_id': 11, 'start_character': 0, 'end_paragraph_id': 11, 'end_character': 291, 'bleu_score': 0.826421396368441, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9875693944349445371}, 'section': 'Section::::Advantages.\n'}]}]