南极洲气候严寒的最主要原因是( )
A:地处高纬地区
B:海洋水温低
C:有巨厚冰层
D:高原地形
费老师在介绍我国古代某一朝代市民生活的讲座中,多次提及“瓦子”“勾栏”。由此推断,这一朝代应是( )
用所给词的适当形式填空
(1)My mother often ____ (read) books after work.
(2)The boy ____ (ride) a bike to school every day.
(3)Mum always ____ (wash) clothes on Saturday.
(4)Li Kai ____(have)a cool bag.
(5)My father never ____ (go) to work late.
已知a,b,c为△ABC的三边长,且满足a2c2﹣b2c2=a4﹣b4,判断△ABC的形状( )