完形填空。

     This i______ (1) a classroom. It is nice a______(2) bright, but it is s______ (3). The doors and w______(4) are clean. The desks and chairs are clean, t______(5). The walls are white. O______(6) the front wall there is a b______(72). The teacher’s desk is near it. On the desk there are s______(8) flowers and pencils. There is a clock on the wall. It’s not old. It is n______(9).Now there are o______(10) eight students in the room. They are cleaning the classroom.

28.

翼墙式隧道洞门主要由端墙和翼墙组成。其中（）用来保证仰坡上的雨水和落石不致掉到线路上。它以10：1的坡度向洞身倾斜。