结合上下文及所给首字母填空

    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  7  . 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.

在吹灰程序控制系统中，一般不允许在低负荷下吹扫，故通常具有低负荷闭锁功能。