The Sports Medicine Programs of the Olympic Training Center, a complex where final tryouts are held for athletes representing the United States in the Olympics, is geared toward enhancing athletes' performance and toward their preparation for international competition.
moreover C means: to enhance the performance and (to enhance) the preparation. It's awkward to say 'to enhance the preparation', isn't it? This distorts the logic of the sentence. The correct paralellism should be like that in E: geared toward enhancing the performance and (toward) preparing them....