单选题 Many people believe the glare from snow causes snow blindness. Yet, dark glasses or not they find themselves suffering from headaches and watering eyes, and even snowblindness, when exposed to several hours of "snow light".
The United States Army has now determined that the glare from snow does not cause snow-blindness in troops in a snow-covered country. Rather, a man's eyes frequently find nothing to focus on in a broad expanse of a snow-covered area So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at. Finding nothing, hour after hour, the eyes never stop searching and the eyeballs become sore and the eye muscle aches. Nature balances this annoyance by producing more and more liquid which covers the eyeballs. The liquid covers the eyeballs in increasing quantity until vision blurs. And the result is total, even though temporary, snowblindness.
Experiments led the Army to a simple method of overcoming this problem. Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape. Even the scouts themselves throw lightweight, dark-colored objects ahead on which they too can focus. The men following can then see something. Their gaze is arrested. Their eyes focus on a bush and having found something to see, stop searching through the snow-blanketed landscape. By focusing their attention on one object at a time, the man can cross the snow without becoming hopelessly snowblind or lost. In this way the problem of crossing a solid white area is overcome.

问答题 The eyeballs become sore and the eye muscles ache because______.
A. tears cover the eyeballs B. the eyes are annoyed by blinding sunlight
C. the eyes are annoyed by blinding snow D. there is nothing to focus on

问答题 When the eyes are sore, tears are produced to______.
A. clear the vision B. remedy snowblindness
C. ease the annoyance D. loosen the muscles

单选题 Snow-blindness may be avoided by______.
A. concentration on the solid white area
B. providing the eyes with something to focus on
C. searching for something to look at in snow-covered areas
D. covering the eyeballs with liquid

单选题 The first paragraph is mainly concerned with______.
A. snow glare and snow blindness B. the whiteness from snow
C. headaches, watering eyes and snowb lindness D. the need for dark glasses

单选题 A suitable title for this passage would be______.
A. Snowblindness and How to Overcome It B. Nature' s Cure for Snowblindness
C. Soldiers in the Snow D. Snow Vision