阅读下面材料，在空白处填入适当的内容（不多于3个单词）或括号内单词的正确形式。
Many teachers believe that the responsibilities for learning lie with the student. ____ a long reading assignment is given, instructors expect students to be familiar with ____ (inform) in the reading even if they do not discuss it in class or take an examination. The ideal student is considered to be one who is motivated to learn for the sake of learning, not the one interested only in getting high grades. Sometimes homework is returned ____ brief written comments but without a grade. Even if a grade is not given, the student is ____ (responsibility) for learning the material assigned. When research ____ (assign), the professor expects the student to take it actively and to complete it with minimum guidance. It is the student's responsibility to find books, magazines, and articles in the library. Professors do not have the time to explain ____ a university library works; they expect students, ____ (especial) graduate students, to be able to exhaust the reference origins in the library. Professors will help students who need it, but prefer that their students should not be too dependent on them. In the United States, professors have many other duties ____ teaching, such as administrative or research work. Therefore, the time ____ a professor can spend with a student outside of class ____ (limit). If a student has problems with classroom work, the student should either approach a professor during office hours or make an appointment.
