如图,直线a,b相交于点O,若∠1等于40°,则∠2等于( )
A:140°
B:120°
C:60°
D:50°
学校召开家长会,请了280位家长,8人围坐一桌,需准备多少张桌子?
—What's your idea about family education?
— kids learn to be independent, it is for their future.