题目

May is National Bike Month. a month-long event trying to get couch potatoes outside, cars off the roads and subway trains empty. It encourages everyone to get back onto their bicycles to enjoy riding a bike an often as they can during the month (and hopefully longer). May in the beginning summer and warm weather, so why not start right away and enjoy sunshine!Ride Out to Protect the EnvironmentBike month helps everyone make their efforts to improve theenvironment. If you’rebiking to school, you are helping bring down the air pollution. It is the most common form of pollution andby getting yo在课题学习后，同学们为教室窗户设计一个遮阳蓬，小明同学绘制的设计图如图所示，其中，AB表示窗户，且AB=2.82米，△BCD表示直角遮阳蓬，已知当地一年中在午时的太阳光与水平线CD的最小夹角α为18°，最大夹角β为66°，根据以上数据，计算出遮阳蓬中CD的长是（结果精确到0.1）（参考数据：sin18°≈0.31，tan18°≈0.32，sin66°≈0.91，tan66°≈2.2）（　　）A．1.2米B．1.5米C．1.9米D．2.5米