Pied-piping in A-bar extraction represents a straightforward case of cross-linguistic variation within certain limits. For example, there are some languages, like English, which can ask wh-questions like the one in (1a); many more languages that can ask the wh-question in (1b); and (1c) is apparently unattested:
(1) a. [Who] are you talking with?
b. [With whom] are you talking?
c. *[Talking with whom] are you?
Cable (2007, 2010) introduced the functional projection QP, which dominates ...