The secondary carbocation shown undergoes a single 1,2-hydride shift to give a cation stabilised by the aromatic ring. Which structure shown is the cation formed?

The cation shown is the 1-phenylpropan-2-yl cation. A hydride moves from the benzylic CH${}_2$ to the adjacent cationic carbon, which places the charge on the benzylic carbon. The product is the 1-phenylpropyl cation, a benzylic cation stabilised by resonance with the ring, much more stable than the unconjugated secondary cation.