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  • A wh-expression without wh-movement, where the wh-word is the object of the preposition “about”:

    You are talking about what?

  • A sentence that has undergone wh-movement:

    What are you talking about?

  • ⸺with a pied-piped “about”:

    About what are you talking?

  • A question — This doesn’t seem acceptable; why can’t the “talking” get pied-piped as well? Or, can it?

    Talking about what are you?


Similarly (I find),

From Google search results

  • A wh-expression without wh-movement, where the wh-word is the object of the preposition “of”:

    Chills and headache are symptoms of what?

  • That above, with wh-movement applied:

    What are chills and headache symptoms of?

  • ⸺with a pied-piped “of”. A question — Is this structure acceptable? Why, or why not?

    Of what are chills and headache symptoms?

  • The entire wh-clause has gotten pied-piped:

    Symptoms of what are chills and headache?


Why can’t “-ing about” get pied-piped in wh-movement when “(noun) of” can be? What exactly determines what can be pied-piped and what cannot in wh-movement?

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