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  3. Many people believe the glare from snow

Many people believe the glare from snow

恬恬2019-12-17  20
问题 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 snow-blindness, when exposed to several hours of "snow light". The United States Army has now determined that 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 barren snow-covered terrain. 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 muscles ache. Nature offsets this irritation by producing more and fluid which covers the eyeball. The fluid covers the eyeball in increasing quantity until vision blurs,then is observed, and the result is total, even though temporary, snow-blindness. 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 scouring the snow-blanketed landscape. By focusing their attention on one object at a time, the men can cross the snow without becoming hopelessly snow-blind or lost. In this way the problem of crossing a solid white terrain is overcome.Snow-blindness may be avoided by_________.
选项 A. concentrating to the solid white terrainB. searching for something to look at in snow-covered terrainC. providing the eyes with something to focus onD. covering the eyeballs with fluid
答案C
解析根据第二段可知，雪盲症的发生最根本的原因是茫茫雪原上没有除了白色以外的颜色 可以看到．因而眼睛疲劳，因此提供可以聚焦的物体是根本预防办法，故选C。
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