Question: what are the two most common elements in the solar system
[{'answer': 'Hydrogen', 'provenance': [{'wikipedia_id': '392828', 'title': 'Abundance of the chemical elements', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 8, 'bleu_score': 1.0, 'section': 'Section::::Universe.\n'}]}, {'answer': 'Helium', 'provenance': [{'wikipedia_id': '392828', 'title': 'Abundance of the chemical elements', 'start_paragraph_id': 2, 'start_character': 347, 'end_paragraph_id': 2, 'end_character': 353, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]