Which is a complete sentence?
a. roosevelt arch, the first major entrance.
b. yellowstone park sits on a dormant volcano.
c. to capture breathtaking views.
d. a less traveled route to lone star geyser.

B. Yellowstone Park sits on a dormant volcano.

It is a complete sentence because it has a subject, a verb, and it expresses a complete thought.

Its subject is Yellowstone Park. Its verb is sits. It expresses a complete thought, meaning it does not give rise to questions.

choice a - only has a subject
choice c - dependent clause, gives rise to the question "why?" like why are we here? we are here to capture breathtaking views.
choice d - dependent clause. gives rise to the question "what?". like what is a less traveled route to Lone Star Geyser? Blank bridge is a less traveled route to Lone Star Geyser.