THE TREND: Short THE KEY PIECE: Rayon shorts, BCBGeneration, $58; bcbgeneration.com. WHY THIS WORKS: Showing only leg keeps the style sophisticated. SHOP THE LOOK: A Necklace, Tomoko Igarashi, $200; tomokoigarashi.com. B Blazer, Rebecca Minkoff, $365; shopbop.com. C Watch, AK Anne Klein, $75; zappos.com. D Sandals, J.Crew, $198; jcrew.com. E Tank, Lutz and Patmos, $355; 212-876-1368.