 The position of the "wh"-word across the matrix clauses (a-trees) and the embedded clauses (b-trees) captures the difference in word order.Matrix "wh"-clauses have V2 word order, whereas embedded wh-clauses have (what amounts to) V3 word order.In the matrix clauses, the "wh"-word is a dependent of the finite verb, whereas it is the head over the finite verb in the embedded "wh"-clauses.