A:分封制代替禅让制
B:分封制代替世袭制
C:禅让制仍在继续
D:王位世袭制代替禅让制
Driving in the mountains can be very dangerous. You can't be ______careful.
已知抛物线y2=4x,焦点为P,平面上一定点A(m,0),满足OA→=2PA→,过A作直线l,过原点作l的垂线,垂足为Q,则Q的轨迹方程为( )
下列划线字的注音,完全正确的一项是( )
22.62÷7.2-(12.7-8.9)=____
(得数保留两位小数)