This condition accounts for the ungrammaticality of sentences like (i) and (ii), where a wh-phrase has been extracted from the adjunct a.
(i) *Which concert did you sleep [a during t]?
(ii) *How did you leave [a before fixing the car t]?
- Chomsky, Noam A. 1986b. Barriers. MIT Press, Cambridge, Mass.
- Huang, James. 1982. Move wh in a language without wh-movement. Linguistic review, 369-416.
- Rizzi, L. 1990. Relativized Minimality. MIT Press, Cambridge, Mass.