单选题 The main purpose of this text is to ______.

A、 explain about the rating system of American movies
B、 emphasize the role of parents on guiding their children to suitable films
C、 explain why children like horror movies
D、 analyze the mysteries of youth and violence

【正确答案】 B

【答案解析】[解析] 主旨题。由最后一段中的the real responsibility for limiting children's access rests with the parents可知，解释美国电影分级制度是为了进一步说明电影中可能存在不适宜观看的内容，所以家长应该重视指导子女观看合适的影片。