Question: when did the us join the allied powers
[{'answer': 'December 1941', 'provenance': [{'wikipedia_id': '2198844', 'title': 'Allies of World War II', 'start_paragraph_id': 2, 'start_character': 743, 'end_paragraph_id': 2, 'end_character': 756, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '2198844', 'title': 'Allies of World War II', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 939, 'bleu_score': 0.913511096010105, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7855900252327624803}, 'section': 'Section::::Abstract.'}]}]