A：whether light goes faster than sound
B：how many colors were there in a rainbow
C：that the moon travels around the earth
D：what would the world be like in the future
若实数a、b满足（a﹣2）2+ b−2a =0，求b+2a的值．
我国藏族同胞穿藏袍，主要是为了适应青藏地区的（ ）
