第4题: [单项选择]When Edison died, it was proposed that the Americans ______ all power in their homes, streets and factories for several minutes in honor of this great man. A. turn off B. turned off C. must turned off D. would have turned off 参考答案:A 答案解析:it is proposed that后面要使用虚拟语气——(should)+动词原形,因此选A。