Predicate adjective relates to subject of the sentence, and modifies it. In A the subject is I, adjective "first" does not relate to it. In B the subject is The teacher, "angry" is an adjective which relates to it, and modifies the subject. In C the subject is You, adjective "hard" does not relate to it. In D the subject is We, adjective "distant" does not relate to it. So B is true.
The sentence containing a predicate adjective is B: "The teacher appeared angry when Dave forgot his homework." In this sentence, 'angry' describes the subject 'The teacher' through the linking verb 'appeared.' Therefore, it functions as a predicate adjective.
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