Dad , why should I stop ____ computer games ? For your health , my boy , I'm afraid you _______ .
A:to play; must
B:playing; have to
C:to play ; can
D:playing ; may
已知向量m→=(λ+1,1),n→=(λ+2,2),若(m→+n→)⊥(m→-n→),则λ= ( )
如图,已知A、B、C、D、E均在⊙O上,且AC为⊙O的直径,则∠A+∠B+∠C=____度.
一个两位数x,还有一个两位数y,若把两位数x放在y前面,组成一个四位数,则这个四位数为( )
1 often take a bus to school, but I go to school by bike.