A:恒星与星云
B:恒星与行星
C:行星与卫星
D:行星与星云
(4.5×99+5.5×99)×2.7=____
Many people are playing games on the beach. Some are playing volleyball, _______ are playing soccer.
求作:等腰△PBD,使线段BD为等腰△PBD的底边,点P在∠ABC内部,且点P到∠ABC两边的距离相等.
腌肉长时间不易腐败,主要原因是( )
下列有关科学实验与方法的叙述正确的是( )