[4/(a^2？ 4)+ 1/(2? a)]w =[4/(a+2)(a-2)-(a+2)/(a+2)(a-2)]w =(2-a)w/(a+2)(a-2)=-w/(a+2)= 1

So w=-a-2 and a+2 ≠ 0 = > A≦-2. Choose D.

What you said about a≠2 is also right, but this question asks about the value of W, so I don't care about the value of A. If it is more rigorous, we should add W≦-4 to make W =-a-2(a≦-2 and W≦-4).