A predicate nominative will never be in a prepositional phrase. A direct object receives the action performed by the subject. The verb is always an action verb . Another way of saying it is that the subject does the verb to the direct object. To find the direct object , say the subject and verb followed by whom or what.
Tree answers the question so tree is the direct object.
If nothing answers the question whom or what , you know that there is no direct object. Nothing answers the question so the sentence has no direct object . The direct object must be a noun or pronoun. A direct object will never be in a prepositional phrase. Find the subjects, verbs, predicate nominatives, and direct objects in these sentences.