What are the only countries in Africa that speak English as a first language and not another language?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'QUESTIONS_ENTITY', 'name_': 'Q1860', 'id': 0, 'label': 'English'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q5107', 'id': 1, 'label': 'continent'}, {'type': 'QUESTIONS_ENTITY', 'name_': 'Q15', 'id': 2, 'label': 'Africa'}, {'type': 'INTERNAL', 'name_': 'Q48', 'id': 3, 'label': 'Asia'}, {'type': 'INTERNAL', 'name_': 'Q51880383', 'id': 4, 'label': 'Behind The Voice Actors'}], 'links': [{'name_': 'P31', 'source': 3, 'target': 1, 'label': 'instance of'}, {'name_': 'P47', 'source': 3, 'target': 2, 'label': 'shares border with'}, {'name_': 'P407', 'source': 4, 'target': 0, 'label': 'language of work or name'}, {'name_': 'P1687', 'source': 4, 'target': 1, 'label': 'Wikidata property'}]}