单选题 It (is requested) (that) every student (writes) a paper (on) sustainable development.
【正确答案】 C
【答案解析】[解析] 应改为write或should write。句中谓语动词是request的被动语态形式,因此其主语从句需用虚拟式动词,即谓语动词用原形或者should+动词原形。句意:每位学生被要求写一篇有关可持续发展的论文。