单项选择题 根据Document doc=new News();可以判断选项（ ）语法上是错误的。

单项选择题 The Tang Dynasty was an era of extensive cultural exchange betweenChina and the world. The products and artifacts of the ancientcivilizations in the world gathered in ( ).

问答题 羊毛和蚕丝主要组成成分是[填空(1)] 。