题目

阅读文章回答问题 This is Hong Kong Middle School. It is very big and beautiful. There are 34 classes, 300 teachers and 3, 500 students in the school. In the middle of the school there is a tall building. It's for us to have classes. All the classrooms are there. There are some small rooms, too. They are offices for the teachers to work. All the teachers get ready for their lessons there. In front of the tall building, there is a small one. It is the library. There are many books there. The teachers and the students like to read books in it. Sometimes they borrow(借)books from it. Ther呼气时，膈肌的变化情况（ ）A．膈肌舒张，膈顶部上升 B．膈肌收缩，膈顶部上升C．膈肌舒张，膈顶部下降 D．膈肌收缩，膈顶部下降