阅读理解题为6-10题，请按顺序作答。阅读理解：Directions：Read the following passages carefully. Each passage is followed by some questions or unfinished sentences. For each of them there are four choices marked A, B, C, and D. Choose the best answer to each question.　　School buildings themselves can show liberal (开明的) or conservative views about what should go on in a classroom. The earliest schools had separate classrooms for different grades. The rooms were laid out formally, with pupils’ desks fastened to the floor in straight rows facing the teacher’s desk. Clearly, such schools reflected a teacher-and-subject-centered view of education.　 Schools of the next generation had more open space, and most had movable desks. They also often provided special rooms or areas for science, art, music, and physical education. There were still separate rooms for different grade levels, however, and the desks still were likely to be formally arranged. That is, the schoolroom was still largely designed to carry out the old-school program, which involved grade levels, uniform time blocks, and study of subject matters. Newer subjects, not newer teaching methods, accounted for most of what was new in school design.　 The first school buildings constructed to encourage liberal teaching methods appeared in the mid-1950s. Folding interior (内部的) walls permitted the flexible use of space to encourage large-group, small-group, or individual instruction. Some provided carrels for individual study, areas for team teaching, and centers for programmed instruction.　 In the newest buildings called open schools, the use of space is even more flexible. Areas within the buildings can be readily expanded for program changes, and used for many kinds of functions. One should remember, though, the physical layout (布局) of a school cannot decide whether it has the conservative or liberal teaching practices. What determines whether the classroom is liberal or conservative is the spirit and attitude of the teacher.What is the main idea of this passage?