Question: where does diffusion occur in the excretory system
[{'answer': 'diffusion', 'provenance': [{'wikipedia_id': '149769', 'title': 'Excretory system', 'start_paragraph_id': 28, 'start_character': 254, 'end_paragraph_id': 28, 'end_character': 263, 'bleu_score': 1.0, 'section': 'Section::::Systems.:Biliary system.\n'}]}, {'provenance': [{'wikipedia_id': '149769', 'title': 'Excretory system', 'start_paragraph_id': 28, 'start_character': 0, 'end_paragraph_id': 28, 'end_character': 280, 'bleu_score': 0.955027111100031, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15622739344130100268}, 'section': 'Section::::Systems.:Biliary system.\n'}]}]