题目

阅读下面短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。Howeverobjective we believe ourselves to be, most of us do not judge a product only onthe basis of its advantages; we don't only 1 its quality, value or style before making adecision. 2 ， we are easilyinfluenced by the people around us.Thereis nothing 3 with this. It is probably a smarter way tomake decisions than relying on only our own 4.But it does make life hard for companies. They have long understood that groupsof friends and relatives 5 to buy the same products, but understandingthe 6 has been如图，四边形ABCD内接于⊙O，BD是⊙O的直径，AE⊥CD交CD的延长线于点E，DA=DC，∠DBC=30°，DC=4cm．（1）求BD的长；（2）求图中阴影部分的面积．（结果保留根号和π）