互动封闭仿真课堂
1、智能交互 2、电子板书式视频教学 3、在线互动问答 4、封闭课堂启发式教学方式
随堂测试、知识梳理、易错点揭示、总结启迪智能错题本
听课中的错题能自动加入错题本，课后可方便复习及导出错题本升级服务
在线答疑、课后同类题练习、讲义下载、短信提醒原则五、介词后跟-ing形式，可以在-ing前加逻辑主语
例9. The discovery of new evidence led to ______________.
A. the thief having been caught B. the thief to be caught
C. catch the thief D. the thief being caught
解析：本题led to中的to是介词，后面应该用-ing形式，the thief作-ing的逻辑主语，所以答案为D。
例10. At the beginning of class, the noise of desks ____ could be heard outside the classroom.
A. opened and closed B. to be opened and closed
C. being opened and closed D. to open and close
解析：本题the noise of中的of是介词，后面应该用-ing形式，desks作-ing的逻辑主语，所以答案为C。
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