①吸入的空气②细胞③动脉血④静脉血⑤肺泡.
A:①②③④⑤
B:①⑤③④②
C:④③⑤①②
D:②④③⑤①
集合A=x|-2<x<2,B=x|x2-2x≤0,则A∩B=( )
China has a large population, people can everywhere.
如图所示,圆O的直径AB=6,C为圆周上一点,BC=3过C作圆的切线l,过A作l的垂线AD,垂足为D,则∠DAC=( )