A:①②
B:①③
C:②④
D:③④
①全部位于北半球,大部分位于东半球 ②地跨热带、温带、寒带 ③温带大陆性气候分布广,季风气候只分布在东亚 ④地势中部高、四周低,河流呈辐射状流向四周海洋
数列{an}中,已知对任意n∈N*,a1+a2+a3+…+an=3n﹣1,则a12+a22+a32+…+an2等于( )
关于三江源地区的说法不正确的是( )
铁有三种常见的氧化物:FeO、Fe2O3、Fe3O4.现有某铁的氧化物样品,已知其中铁元素与氧元素的质量比是21:8,关于该样品的说法正确的是( )
A: Can I help you?
B: Yes. The green scarf is very pretty. How much is it?
A: It's $100.
B: It's too expensive. What about the sunglasses?
A: They're $20.
B: They're cheap. I like them.