单选题 Although most universities in the United States are on a semester system which offers classes in the fall and spring some schools ______ a quarter system comprised of spring, fall, winter, and summer quarters.
A. manipulate B. stipulate C. regulate D. observe

【正确答案】 C

【答案解析】[解析] 句子大意为：尽管美国大部分大学的课程分为秋冬两季，一些学校却管理着四季课程的系统。在给出的选项中：manipulate“利用”；stipulate“规定”；regulate“管理”； observe“遵守”。所以，正确答案是C。