A:①②
B:①③
C:②④
D:③④
随地吐痰易传播疾病,痰形成于( )
如图在△ABC中,∠C=90°,BE是∠CBD的平分线,DE⊥BE交AB于点D,圆O是△BDE外接圆.
(Ⅰ)求证:AC是圆O的切线;
(Ⅱ)如果AD=6,AE=62,求BC的长.
It's impolite____ ____during a meal in France.