Question: what type of bond joins the nitrogenous bases in dna
[{'answer': 'hydrogen bonds', 'provenance': [{'wikipedia_id': '1393654', 'title': 'Nitrogenous base', 'start_paragraph_id': 4, 'start_character': 645, 'end_paragraph_id': 4, 'end_character': 659, 'bleu_score': 1.0, 'section': 'Section::::Role in nucleic acids.\n'}]}, {'provenance': [{'wikipedia_id': '1393654', 'title': 'Nitrogenous base', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 972, 'bleu_score': 0.7915651031967781, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16219455529374676790}, 'section': 'Section::::Role in nucleic acids.\n'}]}]