Which word in the sentence is the predicate nominative?

Her pet is a moody gray cat.

a. gray

b. cat

c. moody

d. pet

Cat.

A predicate nominative is a noun or pronoun that follows the verb and describes or renames the subject.

Noun or Pronoun: This rules out gray and moody

Follows the verb: -

Renames the subject: The subject is her pet. So, the answer is cat.