Final answer:
In the sentence provided, 'Leroy', 'Jenna', and 'castle' are nouns. The word 'old' is an adjective that modifies the noun 'castle'.
Step-by-step explanation:
In the sentence, 'Leroy and Jenna walked up to an old castle', 'Leroy', 'Jenna', and 'castle' are nouns as they represent people or a place. The word 'old' is an adjective because it describes the noun 'castle'. An adjective describes or modifies a noun or a pronoun, while a noun is a word for a person, place, or thing.
Learn more about Nouns and Adjectives