Question: what were the two reasons why the us joined the allies in 1917
[{'answer': 'unrestricted submarine warfare', 'provenance': [{'wikipedia_id': '25162935', 'title': 'American entry into World War I', 'start_paragraph_id': 4, 'start_character': 293, 'end_paragraph_id': 4, 'end_character': 323, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Zimmermann Telegram', 'provenance': [{'wikipedia_id': '25162935', 'title': 'American entry into World War I', 'start_paragraph_id': 5, 'start_character': 136, 'end_paragraph_id': 5, 'end_character': 155, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]