Question: the upper layer of soil called horizon a is where
[{'answer': 'the very top layer', 'provenance': [{'wikipedia_id': '525538', 'title': 'Topsoil', 'start_paragraph_id': 5, 'start_character': 99, 'end_paragraph_id': 5, 'end_character': 117, 'bleu_score': 1.0, 'section': 'Section::::Classification.\n'}]}, {'provenance': [{'wikipedia_id': '525538', 'title': 'Topsoil', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 117, 'bleu_score': 0.9067110266941041, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6871813015430531294}, 'section': 'Section::::Classification.\n'}]}]