题目内容：

The first textbook _________for teaching English as a foreign language came out in the 16th century.
我还是不懂啊.

优质解答

The first textbooks written for teaching english as a foreign language came out in the 16th century.
将英语作为外语的第一本教科书是16世纪编辑出版的.
written for teaching english as a foreign language是后置定语,修饰名词textbooks,textbooks与written是被动关系,而且written这个动作是过去的动作,所以write这个词要用过去分词的形式表示被动和完成.

追问：

可是 to be written 呢？？

追答：

仅仅一个written表示被动和完成，换言之，表示被动，时间上是过去。 to be written 也表示被动，但时间上是将来。 being written表示被动，时间上是正在进行。