若集合M = {x ∈R | 2 ^x ≥ 4}，N = {x∈R | x ²－4 x+3 ≥0}，则M∩N =(    )

A：{x | x≤ 4}

B：{x | x≤ 1}

C：{x | x≥ 2}

D：{x | x≥ 3}