Final answer:
The predicate nominative in the sentence is 'agricultural innovator,' as it follows the linking verb 'became' and identifies George Washington Carver.
Step-by-step explanation:
In the sentence "George Washington Carver, the son of slaves, became an agricultural innovator," the predicate nominative is "agricultural innovator." A predicate nominative is a noun or pronoun that follows a linking verb and renames, identifies, or explains the subject of the sentence. Here, the linking verb is "became," and "agricultural innovator" renames or identifies George Washington Carver. Predicate nominatives are essential to understanding the subject more fully in a sentence.