Why do you like winter?
A:Because I like snow.
B:Because I can go on a picnic.
A maths book and five ____(notebook/notebooks).
Cholera was a ____(致命的) disease. Many people died of it in the past .
①主体 ②法律事实 ③内容 ④客体
已知映射f:A→B,其中A=B=R,对应法则f:x→y=x2-2x+2若对实数k∈B,在集合A中不存在原象,则k的取值范围是 ( )