Answer:
D. the executive summary
Step-by-step explanation:
Front matter is the initial part of a report and comprises the following: title page, abstract, table of contents, list of figures etc.
The executive summary just like the abstract is a front matter because another definition of front matter is that they are always prepared after the other parts of the report has been concluded; and this holds true for the executive summary.
Lastly, 'front matter' also gets their name from the position they occupy in a report, and executive summary falls into that category.