A:①②③
B:①③④
C:①②④
D:②③④
下列属于我国基本国策的有( )
①对外开放 ②科教兴国 ③计划生育 ④保护环境
若集合M = {x ∈R | 2 x ≥ 4},N = {x∈R | x 2-4 x+3 ≥0},则M∩N =( )
—Really? That's interesting!