In the sentence "Coffee beans from Costa Rica taste unique because of the volcanic ash incorporated into the soil where they grow":
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Linking verb: "taste" (Here, "taste" acts as a linking verb that connects the subject "Coffee beans from Costa Rica" to the predicate adjective "unique.")
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Predicate adjective: "unique" (It describes the subject and follows the linking verb.)
So, "taste" is the linking verb, and "unique" is the predicate adjective.