Question: when did the cross become a symbol of christianity
[{'answer': 'from the 4th century', 'provenance': [{'wikipedia_id': '27484195', 'title': 'Christian cross', 'start_paragraph_id': 7, 'start_character': 484, 'end_paragraph_id': 7, 'end_character': 504, 'bleu_score': 1.0, 'section': 'Section::::History.:Early Christian usage.\n'}]}, {'provenance': [{'wikipedia_id': '27484195', 'title': 'Christian cross', 'start_paragraph_id': 7, 'start_character': 0, 'end_paragraph_id': 7, 'end_character': 504, 'bleu_score': 0.741385419374419, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13674766353292430345}, 'section': 'Section::::History.:Early Christian usage.\n'}]}]