Xiao Qing is my friend. He is thirteen years old. He is in a big school. There is a playground in the middle of his school. The red classroom building is on its left and on its right is the library. Behind the playground is the dining hall. Xiao Qing and his classmates have lunch there from Monday to Friday. Every day they can eat meat. Today is Friday. They eat beef .There is soup, on Wednesday. It's Xiao Qing's favourite. Basketball is his favourite sport. He plays it on Tuesday and Thursday afternoon. But his classmates play football and jianzi. Today is Xiao Qing's birthday. He wants a football. So he can play it with his classmates.

若直线x=1的倾斜角为α，则α（　　）

如图为我国部分经济作物主要分布区示意图，图中①、②表示的经济作物分别是（  ）

 ①以原点O为对称中心，画出△ABC关于原点O对称的△A₁B₁C₁，并写出B₁的坐标；

 ②再把△A₁B₁C₁绕点C₁，顺时针旋转90°，得到△A₂B₂C₂，请你画出△A₂B₂C₂，并写出B₂的坐标．