The answer to your question is the it’s climate
The option which is a fragment in this paragraph is the first one - Because frustrated students have been pushing for renovations so their gym can accommodate larger crowds.
It is a fragment because it is incomplete - it cannot stand on its own.
The answer would be C, because an independent clause should be just a simple sentence; when two are separated by a semicolon, that would make sense, but if it were two dependent clauses, that wouldn't make sense.
So, it would be C.
