也许我也应该说这些是在不同的pptx文件中。 它的用途是让用户从树中选择他们想要放入合并文件的演示文稿。 所以我们正在尝试合并他们选择的文件。 可以
为1. 可以达到20个。 上面的文章显然遗漏了一些东西，我试图找出它是什么。

maybe I should also say that these are in different pptx files.  what it's for is we are letting the users select what presentations they want to put in the merged file from a tree.  so we are trying to merge the files they select.  can be 1.  can be up to 20.  the article above is obviously missing something and I'm trying to find out what it is.