Question: at what age does the thymus reach its maximal size
[{'answer': 'puberty', 'provenance': [{'wikipedia_id': '56265', 'title': 'Thymus', 'start_paragraph_id': 24, 'start_character': 451, 'end_paragraph_id': 24, 'end_character': 458, 'bleu_score': 1.0, 'section': 'Section::::Development.:Involution.\n'}]}]