Answer
The axis of the Polaroid filter should be vertical.
Work Step by Step
If the reflective surface is nonmetallic, much of the reflected light is polarized. The polarization direction is parallel to the direction of the reflecting surface.
This is discussed on page 556, and diagrammed in Figure 29.33.
In this case, the polished floor is a horizontal plane, so the reflected light (glare) is polarized horizontally. Sunglasses with vertically-oriented polarization axes filter out the glare.
