Final answer:
A predicate adjective is dominant over a predicate nominative when it is used to describe the subject, making option C the correct answer. It is not about dominance but the function that each serves in a sentence.
Step-by-step explanation:
In English grammar, a predicate adjective is used to describe the subject of a sentence, whereas a predicate nominative follows a linking verb and renames the subject. The question of when a predicate adjective is dominant over a predicate nominative isn't about dominance; it's about the function each serves in a sentence. In general, predicate adjectives are used when describing a subject, which makes option C the correct answer.
Option A is incorrect because predicate adjectives are not always dominant; it depends on what the sentence is conveying. Similarly, Option B is incorrect because possession is typically shown using possessive nouns or pronouns, not predicate adjectives.
Option D is incorrect because it is not that predicate adjectives are never dominant, but rather that whether one is used over the other depends on the function needed in the sentence.