Many people believe the glare from snow causes snow blindness. Yet, with 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 often find nothing to focus on in a broad space of snow-covered without-grass land. So his gaze continually moves and jumps back and forth over the entire landscape in search of something to look at. Finding something, hour after hour, the eyes never stop searching and the eyeballs become tired and the eye muscles ache. Nature makes up for this discomfort by producing more and more fluid (液体) which covers the eyeball. The fluid covers the eyeball in increasing quantity until it makes eyes difficult to see clearly, and the result is total, even though for a short time, snow blindness.

     Experiments lead the Army to a simple method of overcoming this problem. Scouts (侦察员) ahead of the 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 can focus too. 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 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 continuous white land is overcome.

68. To prevent snow blindness caused by the strong light from snow, wearing glasses or not _________.

A. depends on whether the snow is white enough

B. makes no difference

C. makes much difference

D. depends on whether the snow is thick

69. When the eyes are tired, tears flow out __________.

A. to clear the vision            B. to make the eyes stop searching

C. to make the vision unclear     D. to produce more and more liquid

70. Snow blindness can be prevented by ___________

A. moving one’s gaze back and forth

B. walking ahead and keeping looking around

C. making up for the discomfort of one’s eyes

D. providing the eyes with something to focus on

71. What is the probable meaning of the underlined part “Their gaze is arrested.”?

A. They get something to look at.    B. They can only look at one spot.

C. Their eyes are clear.            D. They can’t see freely.

Many people believe the glare from snow causes snow blindness. Yet, with 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 often find nothing to focus on in a broad space of snow-covered without-grass land. So his gaze continually moves and jumps back and forth over the entire landscape in search of something to look at. Finding something, hour after hour, the eyes never stop searching and the eyeballs become tired and the eye muscles ache. Nature makes up for this discomfort by producing more and more fluid (液体) which covers the eyeball. The fluid covers the eyeball in increasing quantity until it makes eyes difficult to see clearly, and the result is total, even though for a short time, snow blindness.

     Experiments lead the Army to a simple method of overcoming this problem. Scouts (侦察员) ahead of the 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 can focus too. 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 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 continuous white land is overcome.

68. To prevent snow blindness caused by the strong light from snow, wearing glasses or not _________.

A. depends on whether the snow is white enough

B. makes no difference

C. makes much difference

D. depends on whether the snow is thick

69. When the eyes are tired, tears flow out __________.

A. to clear the vision            B. to make the eyes stop searching

C. to make the vision unclear     D. to produce more and more liquid

70. Snow blindness can be prevented by ___________

A. moving one’s gaze back and forth

B. walking ahead and keeping looking around

C. making up for the discomfort of one’s eyes

D. providing the eyes with something to focus on

71. What is the probable meaning of the underlined part “Their gaze is arrested.”?

A. They get something to look at.    B. They can only look at one spot.

C. Their eyes are clear.            D. They can’t see freely.