A． concentrating to the solid white terrain
B． searching for something to look at in snow-covered terrain
C． providing the eyes with something to focus on
D． covering the eyeballs with fluid
A． give the men behind something to see
B． beautify the landscape
C． warm themselves in the cold
D． prevent the men behind from losing their way
A． snow-blindness and how to overcome it
B． nature's cure for snow blindness
C． soldiers in the snow
D． snow vision