Please choose the correct ending to complete the given sentence: Health: [header] How to tell if sunglasses are polarized [title] Find a reflective surface that produces glare when light is shining on it. [step] You could use a reflective tabletop, a mirror, or other shiny, flat surface. Make sure the glare is noticeable even from about 2 to 3 feet (60 to 90 cm) away.

Ending1: Prevent other objects from obstructing this glare by placing a piece of clear, colored cloth over the reflective surface. [title] Position the sunglasses so that the gaps of the light source are blocking your view of the lenses. Ending2: Polystyrene is the easiest and cheapest material to use. [substeps] Polystyrene is also sold as plastic, glass, or fabric. Ending3: [substeps] If you need to produce glare, you can turn on overhead lights or shine a flashlight on a reflective surface. [title] Hold your sunglasses about 6 to 8 inches (15 to 20 cm) in front of your eyes. Ending4: You can use a bright, reflective desk lamp with a glare protection window, for example. [substeps] Polarized sunglasses usually have the lens pointed towards the sun.

Answer format: ending1/ending2/ending3/ending4