The correct answer is D) because she enjoys year-round sports. An adverb clause is a subtype of a subordinate clause, meaning that it cannot exist on its own, outside of the main, independent clause.
A cannot be correct because this is not a clause - it doesn't have a finite verb (infinitives, such as 'to live' are non-finite), which means that it is a phrase.
B is a weird sentence fragment, it isn't an adverb clause.
C is also a sentence fragment, the sentence is incomplete.
