Answer: A) It is a proper adjective.
Step-by-step explanation: From the given options, the one that represents why the word "Cherokee" is capitalized in the given sentence, is the corresponding to option A: the word "Cherokee" is a proper adjective specifically representing a member of an American Indian people originally of Tennessee and North Carolina, so, because it is an adjective that describes a person (or group of people) it should be capitalized.