Question: what are the four elements present in dna
[{'answer': 'cytosine ( C )', 'provenance': [{'wikipedia_id': '7955', 'title': 'DNA', 'start_paragraph_id': 10, 'start_character': 379, 'end_paragraph_id': 10, 'end_character': 392, 'bleu_score': 1.0, 'section': 'Section::::Properties.\n'}]}, {'answer': 'guanine ( G )', 'provenance': [{'wikipedia_id': '7955', 'title': 'DNA', 'start_paragraph_id': 10, 'start_character': 393, 'end_paragraph_id': 10, 'end_character': 408, 'bleu_score': 1.0, 'section': 'Section::::Properties.\n'}]}, {'answer': 'adenine ( A )', 'provenance': [{'wikipedia_id': '7955', 'title': 'DNA', 'start_paragraph_id': 10, 'start_character': 366, 'end_paragraph_id': 10, 'end_character': 378, 'bleu_score': 1.0, 'section': 'Section::::Properties.\n'}]}, {'answer': 'thymine ( T )', 'provenance': [{'wikipedia_id': '7955', 'title': 'DNA', 'start_paragraph_id': 10, 'start_character': 409, 'end_paragraph_id': 10, 'end_character': 421, 'bleu_score': 1.0, 'section': 'Section::::Properties.\n'}]}, {'provenance': [{'wikipedia_id': '7955', 'title': 'DNA', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 686, 'bleu_score': 0.9594798946546471, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15919194508319458120}, 'section': 'Section::::Abstract.'}]}]