Question: when is mother's day celebrated in usa
[{'answer': 'Second Sunday in May', 'provenance': [{'wikipedia_id': '1546634', 'title': "Mother's Day (United States)", 'start_paragraph_id': 17, 'start_character': 45, 'end_paragraph_id': 17, 'end_character': 65, 'bleu_score': 1.0, 'section': 'Section::::Spelling.\n'}]}]