Question: what is the diameter of the earth in km
[{'answer': '12,742 kilometres'}, {'provenance': [{'wikipedia_id': '9228', 'title': 'Earth', 'start_paragraph_id': 24, 'start_character': 0, 'end_paragraph_id': 24, 'end_character': 709, 'bleu_score': 0.78243604818153, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12558885358070208978}, 'section': 'Section::::Physical characteristics.:Shape.\n'}]}]