Which code segment should you insert at line 03?

You develop a SharePoint app for a toy company that uses the Representational State Transfer (REST) API for search. The site collections in the app have been crawled recently and use the default search schema.
The app includes the following code segment (Line numbers are included for reference only)

You create the following result sources.

You need to ensure that the app only displays PDF documents.
Which code segment should you insert at line 03?
A.

B.

C.

D.