text: Angle of incidence = angle of reflection.  This also means that a ray will hit the mirror at the midpoint between origin and destination.\n\nSo, \nfor y to see z the ray must hit the mirror 1 meter from it's center.  That puts it at 1/2 meter from the edge so you're OK.  By symmetry y can also see x.\n\nAlso by symmetry, z can see y.  But can z see x?  The ray from x to z (and z to x) must strike the mirror at its midpoint.  \n\nSo, it looks like all three can see the other two.  I think the answer is D provided:\n\nY is standing in front of the center of the mirror, right?