The word sits is used to refer to the action of sit down. On the other hand, the word sets is a word to refer to a group of related objects as a make-up set, tools set, among others. Sometimes the word set is used to refer to the action of place something. According to those definitions, it is possible to affirm that the correct answer is Sits because the sentence mentioned an action made by a cat. So, the correct answer is A. Sits.
