The correct option is B Noun
Nouns refer to persons, places, things or qualities. Here the underlined word 'Italians' refer to the native inhabitants of Italy since Italians refer to people, the word is a noun, therefore, option D is correct. An adjective is a word that modifies the noun that follows since 'Italians' is not followed by any noun, it's not an adjective, option A is incorrect. Adverbs modify adjectives, verbs or other adverbs, 'Italians' do not modify any of these in the sentence. An adverb answers the questions how, why, in what way and so on, whereas the word 'Italians' answers the question who hence it's not an adverb, option B is incorrect. Verbs are words that perform an action since the underlined word does not perform any action, it's not a verb, option C is incorrect.