Question: what level on the ph scale is a solution considered acidic
[{'answer': 'less than 7', 'provenance': [{'wikipedia_id': '24530', 'title': 'PH', 'start_paragraph_id': 2, 'start_character': 307, 'end_paragraph_id': 2, 'end_character': 318, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '24530', 'title': 'PH', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 580, 'bleu_score': 0.559280044794604, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5088261312126045473}, 'section': 'Section::::Abstract.'}]}]