A:①②③
B:①②③④
C:②③④
D:①③④
已知集合A={x∈R|0≤log2x≤2}.
(Ⅰ)若集合B={a2+4a+8,a+3,3log2|﹣a|},且满足B⊆A,求实数a的值;
(Ⅱ)若集合C={y|y=xm,x∈A,m∈R},且满足A∪C=A,求实数m的取值范围.