Why does the phrase "compatibility mode” appear when opening a workbook?

It shows that the original document was saved using an older version of that program.

Explanation:

When workbooks are saved using an older version of the program, it may not be able to display new features in the newer version. This compatibility mode makes it possible to create workbooks that older versions of the program can view perfectly.

the answer is b. executive summary. a management summary, or executive summary, is a short article or section of a document, produced for business purposes, that condenses a longer report or proposal or a group of related reports in such a way that readers can rapidly become familiar with a large body of material without having to read it all.