题目

To get an education, _______.    A. working hard is very important               B. working hard is needed    C. one must work hard                        D. it is needed to work hard 答案：C 解析: 非谓语动词作状语，其逻辑主语要和主句的主语保持一致。to get的逻辑主语应为one(人)。故选C。因式分解：a2﹣6a+9= ．