In a previous exercise, you saw verbs that can function as subjects or complements. Sometimes these verbs can be explained either as part of the verb phrase or as a predicate adjective that describes the subject. Generally speaking, if the focus is on the action of these verbs, the verb is best explained as part of the verb phrase. If the verb functions primarily to describe the condition of the subject, it can be seen as a predicate adjective.
Consider the following sentences:
1. The door was closed by John.Because the first sentence tells us who performed the action of closing the door, the sentence focuses on the action. Thus it is best to see "was closed" as the verb phrase. In the second sentence, however, the important point is not the act of closing the door, but rather the condition of the door when they arrived. Thus in the second sentence we can see "was" as the verb to be underlined and "closed" as a verb that functions as a predicate adjective.
The only way to determine the focus of the third sentence is to see it in context, and even then it might not be clear. In such cases it is best to explain the verb in question as part of the verb phrase. Thus, in the third sentence, "was closed" should be underlined as the verb.
Note that this is a fine point that is not even discussed in many grammar textbooks. In those books, the verbs that here function as predicate adjectives are usually considered as part of the verb phrase. When in doubt, therefore, include the verb in the verb phrase.