Question: what is the si unit of time period
[{'answer': 'the second', 'provenance': [{'wikipedia_id': '10779', 'title': 'Frequency', 'start_paragraph_id': 6, 'start_character': 347, 'end_paragraph_id': 6, 'end_character': 357, 'bleu_score': 1.0, 'section': 'Section::::Units.\n'}]}, {'provenance': [{'wikipedia_id': '10779', 'title': 'Frequency', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 346, 'bleu_score': 0.6106369710458901, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10149233766404499606}, 'section': 'Section::::Units.\n'}]}]