Question: the nation that joined germany and austria-hungary after world war i began was
[{'answer': 'the Ottoman Empire', 'provenance': [{'wikipedia_id': '6673', 'title': 'Central Powers', 'start_paragraph_id': 1, 'start_character': 56, 'end_paragraph_id': 1, 'end_character': 74, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Bulgaria', 'provenance': [{'wikipedia_id': '6673', 'title': 'Central Powers', 'start_paragraph_id': 1, 'start_character': 79, 'end_paragraph_id': 1, 'end_character': 87, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '6673', 'title': 'Central Powers', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 517, 'bleu_score': 0.905645914332555, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 910564917611216589}, 'section': 'Section::::Abstract.'}]}]