In this paper I explain a well-known grammatical contrast that has been studied in the framework of Generative Grammar: the contrast between arguments and adjuncts in the preposition stranding of Wh-Questions. I make use of some recent minimalist studies: the Labeling Algorithm (LA) and the external Pair-Merger analysis based on LA. I also show that the grammaticality of heavy DP shift (HDPS) constructions, which have the same syntactic properties as Wh-questions but do not show the contrast between arguments and adjuncts in preposition stranding, can be adequately explained by the above analysis and some additional assumptions in Phase Theory. Finally, I will show that null operator (NOp) analysis is useful for the grammaticality of parasitic gap (PG) constructions, which at first glance may seem to be an empirical problem for the framework of this paper.
Keywords: external pair-merger; heavy DP shift; labeling algorithm; parasitic gap; preposition stranding.