Which word in the sentence is a predicate nominative? Could you explain why?

1st sentence ---B. prize

2nd sentence ---A. captain

A predicate nominative is a noun or pronoun that renames the subject of the sentence. A predicate nominative follows a linking verb.

In the first sentence, the subject is one . However, from the clause before it, one is understood to refer to medal .

A silver one is the prize for the runner-up.

In the second sentence, the subject is quarterback .

The quarterback of the team will become the captain after this season.