Avalanche and Its Safety An avalanche is a sudden and rapid flow of snow, often mixed with air and water, down a mountainsid

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问题                         Avalanche and Its Safety
    An avalanche is a sudden and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches are【C1】______the biggest dangers in the mountains for both life and property.
    All avalanches are caused by an over-burden of material, typically snowpack, that is too massive and unstable for the slope【C2】______supports it. Determining the critical load, the amount of over-burden which is【C3】______to cause an avalanche, 【C4】______a complex task involving the evaluation of a number of factors.
    Terrain slopes flatter than 25 degrees or steeper than 60 degrees typically have a low 【C5】______of avalanche. Snow does not【C6】______significantly on steep slopes; also, snow does not【C7】______easily on flat slopes. Human-triggered avalanches have the greatest incidence when the snow’s angle of rest is【C8】______35 and 45 degrees; the critical angle, the angle at which the human incidence of avalanches is greatest, is 38 degrees. The rule of thumb is: A slope that is【C9】______enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. Additionally, avalanche risk increases with 【C10】______; that is, the more a slope is disturbed by skiers, the more likely it is that an avalanche will occur.
    Due to the complexity of the subject, winter travelling in the backcountry is never 100% safe. Good avalanche safety is a continuous【C11】______, including route selection and examination of the snowpack, weather【C12】______, and human factors. Several well-known good habits can also 【C13】______the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings should be paid 【C14】______to. Never follow in the tracks of others without your own evaluations; snow conditions are almost certain to have changed since they were made. Observe the terrain and note obvious avalanche paths where plants are 【C15】______or damaged. Avoid travelling below others who might trigger an avalanche.
【C9】

选项 A、thick
B、thin
C、flat
D、rocky

答案C

解析 这个句子说明的是什么样的山坡最易发生雪崩,即A slope that is flat enough to holdsnow but steep enough to ski。flat在此作“平坦”解,与后面的steep形成反义。
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