The core point of this question is to identify the opening sentence that best introduces the topic of expert performance. Option C directly states that it introduces the topic of what makes expert performance, which aligns with the given knowledge point. Option A focuses on the importance of training, which is not directly related to introducing the topic of expert performance. Option B is about highlighting superstars, which is a specific instance rather than an introduction to a general topic. Option D discusses the performance of soccer teams, which is too specific and does not introduce the concept of expert performance. Therefore, the correct answer is C.