A. cooperate with other retirees to carry, out researches B. work on a research topic by their own C. organize various activities on campus D. have classes with college students 参考答案:D 答案解析:[定位] 根据retirement villages定位到原文第三段第四、五句。[解析] 这些社区的居民有权参加学校的多种活动,其中D)与文中的attend classes同义。[避错指导] 这些活动