A Field Exists in Search Results, but Isn't Being Displayed

Multiple Choice

A field exists in search results, but isn't being displayed in the fields sidebar. How can it be added to the fields sidebar?

A) Click All Fields and select the field to add it to Selected Fields.
B) Click Interesting Fields and select the field to add it to Selected Fields.
C) Click Selected Fields and select the field to add it to Interesting Fields.
D) This scenario isn't possible because all fields returned from a search always appear in the fields sidebar.