Xianbin,
You are right, this can be very difficult especially if we don't get these comments until the end of the course. We can use the access system logs of some of the course management systems to monitor if the students are accessing the content we post, but that still does not guarantee that they are really reviewing and studying the material. Another option might be to give them mini assessments throughout the course, like pop-quizzes in a traditional course, to verify that they are reviewing the materials. I hate to do this, but I have had to resort to… >>>