未知题型 一选择题有四个选项，由经验数据可知学生知道答案的概率是0.8。现随机抽取一名学生的试卷，发现该题回答正确，则此学生确实知道正确答案的概率是________。（保留三位有效数字）

未知题型 Clearly present the topic of the research paper you plan to write and publish the next. Although you are encouraged to write the report in English, Chinese presentation is also accepted at this stage. The topic report from can be downloaded from the Week-1 courseware folder.

未知题型 根据我国《物权法》中的规定，简述物权变动的原因。