The word choice is not as precise
A. Short answer
http://www.dictionary.com/browse/objective-test
In my opinion I think D because I would use that answer
B is the most likely answer because the passage shows that the speaker believes in working hard, facing challenges, and working together
The correct answer is sentence (5).
A sentence fragment means that it is only a part of a sentence; it is not complete. Given that it is incomplete, the fragment, aka subordinate/dependent sentence, has to be part of a larger, independent sentence, in order to make any sense. So if you combined sentence (5) with another one, it wouldn't be a fragment anymore.