Which word is a predicate nominative

A ribbon is given to all the runners, but a theophylline is the reward for the winner

The correct answer should be reward

Predicate nominative is basically a noun that is used as a predicate instead of a verb and stands next to copulative verbs such as is. In this case, the example says "theophylline is (the) reward" where you can see reward being the predicate nominative.