Review the passage:
Professor Gregory surveyed the auditorium full of nervous, sweating biochemistry
students. Her gaze often stopped on Bryan. Whose
test anxiety manifested in the loud popping of his knuckles and the high-speed
bouncing of his left leg.
You chose the second part, Her gaze often stopped on Bryan. This part has a main clause: gaze is the subject; stopped is the verb. A fragment will not have a main clause.