I'm currently working on an introductory guide to X-bar Theory for a group of students, and was wondering whether to classify a specific part as a Determiner Phrase or an Adverb Phrase. I have included the sentence in my post. The sentence in question is the interrogative sentence 'Where are my beans?'.
The source material I am using (from years ago) puts the 'where' in a Determiner Phrase, which is kind of odd, since 'where' is supposed to be a relative adverb. I guess the source material uses a DP because a lot of wh-questions use a relative pronoun instead... or am I missing something here? Can anyone enlighten me on why the source material would possible classify 'where' as a DP in X-bar, rather than an Adverb Phrase?