ANIMALS is the word in the sentence that is a plural common noun.
Plural
noun is a word that indicates that there are more than one person,
animal, place, thing, or idea. When you talk of more than one of
anything, you are using the plural nouns. Plural nouns are written using
the same word and simply adding s, es, or ies to the end.
Animal is a singular noun. You add "s" to make it into a plural noun. Thus, ANIMALS.