Question: when was buddhism introduced in sri lanka who introduced it
[{'answer': 'third century BCE', 'provenance': [{'wikipedia_id': '1164480', 'title': 'Buddhism in Sri Lanka', 'start_paragraph_id': 1, 'start_character': 503, 'end_paragraph_id': 1, 'end_character': 520, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Mahinda Bhikkhu , son of Emperor Ashoka'}, {'provenance': [{'wikipedia_id': '1164480', 'title': 'Buddhism in Sri Lanka', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 948, 'bleu_score': 0.8412558115052251, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13895829031792625238}, 'section': 'Section::::History.:Introduction of Buddhism.\n'}]}]