Identify the proper noun in the sentence: "Maria visited Paris last summer."

The correct answer is Maria because she is the name of a specific person, which is the defining characteristic of a proper noun. Proper nouns are unique identifiers for individuals, places, organizations, or sometimes specific events, distinguishing them from common nouns, which refer to general items or concepts. In this sentence, "Maria" serves as a specific reference to a particular individual who visited Paris, making it a proper noun. The sentence also includes the proper noun "Paris," representing a specific place, though that is not the focus here. The other words in the sentence are common nouns or verbs and do not denote specific people, places, or entities.