A:+
B:k-k
C:0
D:k
Officials from China and France formally promised on Thursday to build a new type of economic partnership, while ________ business cooperation.
(Ⅰ)当a=2时,求不等式f(x)<4的解集.
(Ⅱ)当a< 12 时,对于∀x∈(﹣∞,﹣ 12 ,都有f(x)+x≥3成立,求a的取值范围.
射箭运动中使用的弓,其主要制造材料应具备以下哪种物理属性( )