B, you need to give the reader basically a reason to read it so you give the hook and the topic of the sentence so basically what the story is going to be about.
The answer is an adverb clause because "have been" is considered an adverb clause...
Time Safari, Inc. guarantees only B. THE DINOSAURS.
This is a part of the story "A Sound of Thunder", where the character, Eckels, entered the office of Time Safari, Inc. and in a conversation with the company clerk, Eckels found out that the company guarantees nothing but encounters with dinosaurs.
