答案：C

解析：

Choice (C) is correct. This version of the sentence correctly compares the young athlete's accomplishments with her coach's accomplishments, not with her coach. In addition, it uses the plural pronoun "those" to refer to the coach's accomplishments, which allows the noun "coach" to be correctly modified by the noun phrase "a former track star." The possessive noun "coach's" cannot be modified by a noun phrase.