So: "? X0 ∈ [2,4] and x0∈[2 ≤ a "are true propositions,
So 4≤a,
So "? X0 ∈ [2,4], x0∈[2-A ≤ 0 "is true and only if a≥4,
Because the range of a≥4 sufficient and unnecessary condition should be smaller than its range,
So it should be a≥5.
So choose one