A:一千克铁比一千克棉花重
B:小学一节课一般是40分钟
C:10000比9990多1
甲、乙两物体同一时从同一位置自由下落,如果以乙为参照物,则甲的运动状态( )
Kate isn't happy because she lost her pet. Let's go to cheer her up.