New blackboards have been fitted up in all the classrooms.教室里都安装上了新黑板.How many blackboards are there in this room?在这个房间里有几块黑板?Some cleaned the blackboards, others mopped the floor.有些人擦黑板, 有些人拖地板....

n.黑板( blackboard的名词复数 )...

blackboards的音标：...