Answer:
D.
After they watched a documentary film about Africa, Kyle and Missy, who have never traveled before, decided to plan their first overseas trip.
Explanation:
The appositive is a renaming of a noun, something that can be skipped without changing the grammatically and meaning of the sentence.
Here the appositive is "Dr. Walters" - it can be skipped:
My dentist was one of the speakers at Career Day
and it renames "My dentist" - answer B
