'Metaphor' is a literary device / figure of speech in which a word or a phrase is given / applied to an action, object or event where it is not literally applicable. In simpler terms, a metaphor is a comparison that is drawn between two completely unrelated things. In this case, Kate has been compared to a cheetah due to her fast speed, which cannot be literally true. Thus, the correct answer is Option A) - Metaphor. All the remaining options are also literary devices, but they have not been used in the given sentence.