Ordinary sunlight is unpolarised, meaning its electric field vibrates in all directions perpendicular to the direction of travel.

When light reflects off a horizontal non-metallic surface such as water or a road, the reflected light becomes largely horizontally polarised. This concentrated horizontally-vibrating light is what we perceive as harsh glare.

Polaroid (polarising) sunglasses contain a filter whose transmission axis is oriented vertically. This axis blocks the horizontally polarised glare while allowing useful vertically polarised light to pass, so the glare is greatly reduced.

The other options cannot do this: refraction is the mere bending of light, diffraction is the spreading of light around obstacles, and interference is the superposition of waves; none of them selectively removes light vibrating in one particular plane.

Hence, the property that enables sunglasses to cut reflected glare is Polarization.