About four meters long,the room served as a reception hall for important person.
问题描述：
About four meters long,the room served as a reception hall for important person.
About four meters long是什么成分,这是种什么用法.举几个相似的例子最好拓展一下
答
是定语,修饰room,不是什么特殊用法,就是把定语放在前面而已.
比如,About three metres high,the wall is to prevent the *ers from escaping.
定语放前面一是为了给人一个直观的感受,还有就是因为它比较长,放在句中会把主语和谓语分得太远,读起来不连贯.