The default file extension for PowerPoint version 2007 and newer is ?

File extensions identify the format a program uses to save its files, and Microsoft changed the default file format for its Office suite starting with the 2007 version. Before that change, presentation files used a three-letter extension ending in "ppt". From the 2007 version onward, Microsoft switched to a new XML-based format, and the default extension for a presentation file gained an extra letter, becoming a four-letter extension ending in "pptx", where the added "x" signals that the file is stored in the newer XML-based format rather than the older binary format.

The three-letter extension without the added "x" is the correct default only for versions of PowerPoint released before 2007, so it does not match a question specifically asking about 2007 and newer. An extension ending in "pps" was used for a PowerPoint show file that opens directly in slideshow mode rather than in edit mode, which is a different, more specialised file type, not the general default for a saved presentation. The remaining option is not a real Microsoft file extension at all.

When a question specifies "2007 and newer," treat that as a signal to pick the newer XML-based extension with the trailing "x," since Microsoft's file-format naming convention consistently adds an "x" to mark the modern Office Open XML formats (as with .docx and .xlsx as well).