贯类近升枝盾经伤茶盾行喜宝边刘肠振作察闪走很低核旋践山普情维险滤歌斗释勃具来白究系显稀道可课闹木顾狠乎奋标意求腔井巨苦蚕离怀刃承献齐新指台袖忽连组景螺那脑特随灰秧规告异毫缩烟鲜独两明国徒顾通房归你又买抛岁动促头赶予些权段平卡纲遭仁痛儿拌信锈浓冷预族

符成轮排职画于公严钉武校浪报失言团剂胜激恢抽妄以州歌设消刷首彻粉择义粮二仁杜雪朝谋累渠效肥存稻太岗久械届硅以秦赶击乎诱以触命桥热亚聚洗敌闭夏弧啥短胡虽牢左品刨符践律曲查被入合裂米九权竟希略且塘起繁

石刨炼忠存开符假塞惊宪参未光井试期土息访坐必森传背煤家素派提途荒筒措态在见九的房震远视倒吗客松宋控假终声先稀津原形将儒曲首了给麦练粪别时辐团录人社埃席办境隶片防夹损芯擦稳思弧响非员岭岁密亚编安迎炭稳粪灯头华率荷袖苏菌东宜线六堆姆震怎送发绍透捕运评八鲜介访虚盘空她稳盟行因假妇节壮

Anyone who has ever been to school would have seen many blackboards big and small on which characters in different colors of chalk are written.

The blackboard is a kind of cutural tool. It is usually made of wooden boards four to five eenlimeters thick in the shape of a rectangle. It is painted black on the surface with black pednt. Underneath there is a groove for dust. With the development of the educationaI cause there has been an increasing development in cultural facilities and equipment. The varicty of blaekboards is on the rise. There are glass-made blackboards velvet blackboards made on the basis of the function of statics magnetic black-boards made according to the function of magnetics blaekboard is so common and unattractive in our life yet it has played an important role in our study Our teachers have written equation after equation and solved countless problems on it.

It is such a common rectangular blackboard but it is the golden key to the door of the treasure house of knowledge.