Then y ∈ [-7,7]

If the inequality m≥|x+2|-|5-x| holds,

Then ymax≤k means k ≥ 7.

B: ∵ EB and EC are tangents of ∵ O,

∴EB=EC，

∫∠e = 46，

∴∠ECB=∠EBC=67，

∴∠bcd= 180-(∠BCE+∠DCF)= 180-99 = 8 1；

∵ Quadrilateral ADCB is inscribed in⊙ O,

∴∠A+∠BCD= 180，

∴∠A= 180 -8 1 =99。

C: straight line ρcos(θ-π4)=2? Namely. 22ρcosθ+22ρsinθ=2, and the rectangular coordinate equation is x+y-2=0.

The circle ρ=2 means x2+y2=4, and the distance from the center of the circle to the straight line is equal to? |0+0-2|2=2=2 (radius),

So the straight line and the circle are tangent, so the straight line and the circle intersect.

So the answer is: [7, +∞); 99 ; 1.