Question: when did college baseball switch to aluminum bats
[{'answer': '1975', 'provenance': [{'wikipedia_id': '1370306', 'title': 'College baseball', 'start_paragraph_id': 21, 'start_character': 152, 'end_paragraph_id': 21, 'end_character': 156, 'bleu_score': 1.0, 'section': 'Section::::Metal versus wood bat.\n'}]}, {'provenance': [{'wikipedia_id': '1370306', 'title': 'College baseball', 'start_paragraph_id': 21, 'start_character': 0, 'end_paragraph_id': 21, 'end_character': 850, 'bleu_score': 0.9874601949752461, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11840650232290877470}, 'section': 'Section::::Metal versus wood bat.\n'}]}]