题目

If you’re traveling this holiday season, you’ll be doing a lot of standing around. Whether it’s standing in an airport security line or waiting at a crowded gate, it would be nice to take a load off. Better yet, pulling a “seat” out of your back pocket sounds pretty convenient. The Danish company Mono+Mono recently introduced the Sitpack, a seat shaped like a monopod that fits in your pocket when folded up (折叠). Folded up, the Sitpack is 6.6 inches tall and 2.6 inches in diameter (直径). The Sitpack is height-adjustable and can extend to about 34 inches. The seat itself如图，平行四边形ABCD的对角线AC、BD相交于点O，AE平分∠BAD，分别交BC、BD于点E、P，连接OE，∠ADC=60°，AB=BC=1，则下列结论：①∠CAD=30°②BD=③S平行四边形ABCD=AB•AC④OE=AD⑤S△APO=，正确的个数是（　　）A. 2 B. 3 C. 4 D. 5