Avalanche and Its Safety
An avalanche is a sudden and rapid flow of snow,often mixed with air and water,down a anches are 1 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 2 supports rmining the critical load,the amount of over-burden which is 3 to cause an avalanche,4 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 low5 of does not6 significantly on steep slopes;also,snow does not7 easily on fiat n-triggered avalanches have the greatest incidence when the snow's angle of rest 1is 8 35 and 45 degrees;the critical angle,the angle at which the human incidence of avalanches is greatest,is 38 rule of thumb2 is:A slope that is 9 enough to hold snow but steep enough to ski has the potential to generate an avalanche,regardless of the tionally3,avalanche risk increases with 10 ;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 backcountry4 is never 100% avalanche safety is a continuous 11 ,including route selection and examination to the snowpack,weather 12 ,and human ral well-known good habits can also 13 the local authorities issue avalanche risk reports,they should be considered and all warnings should be paid 14 r follow in the tracks of others without your own evaluations;snow conditions are almost certain to have changed since they were rve the terrain and note obvious avalanche paths where plants are 15 or d traveling below others who might trigger an avalanche.
词汇：
avalanche n.雪崩 trigger v.引起，激发
snowpack n.积雪场 incidence n.发生(率)
terrain n.地形，地势 ski v.滑雪
steep adj.险峻的，陡峭的 complexity n.复杂性
注释：
e of rest：这里指积雪保持静止的角度。
b：指“a broadly accurate principle，based on experience or practice rather that theory”，即“通用法则，经验法则”。
tionally：是一个副词，用来引人新的事实或论点，意为“此外”。
country：人烟稀少的地区。
练习：
1.A among B of C to D in
2.A when B that C who D whose
3.A mostly B likely C clearly D surely
4.A are B will be C is D was
5.A weight B form C risk D work
6.A fall B flow C roll D gather
7.A fall B flow C roll D gather
8.A among B between C with D for
9.A thick B thin C flat D rocky
10.A use B time C snow D rain
11.A journey B trip C fact D process
12.A conditions B reports C forecast D event
13.A increase B reduce C improve D remove
14.A price B effort C attention D money
15.A missing B grown C big D fresh
答案与题解：
1.A表达“雪崩是山上可能发生的最大危险之一”的意思，因此应该选择among(在……之中)。
2.B从该句的语法结构上来看，此处需要一个关系代词，代替slope，所以that是最佳选择。选项A、C、D均不符合语法。
3.B选项A不符合语法，c和D符合语法，但不符合常识：过度的雪的积压可能导致雪崩，而不是必定导致雪崩。所以，B是最佳答案。
4.C该句的主语是Determining the critical load，从上下文来看应该使用一般现在时，所以C是正确答案。
5.C要确定本题答案的一个有效的方法是排除法。a.10w weight/form work of avalanche都不合逻辑，只有a low risk of avalanche符合上下文的意思。下面的句子解释了low risk of avalanche的道理，更证实了选risk是正确的。
6.D第6和第7题可以一起考虑。整个句子的意思是：在坡度大的'坡上，雪不会大量堆积。
在较为平坦的坡面，雪不会轻易滑动。
7.B(见6)
8.B理解了句子的意思就不难判断选项：雪在静止状态下，角度在35_45度之间，最可能发生人为触发的雪崩。between：在……之间。
9.C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 hold snow but steep enough to 在此做“平坦”解，与后面的steep形成反义。
10.A句中的that is表明，后半部分是对前半部分的进一步说明。所以，这里的选择要根据下文的意思判断。use是最佳选择，整个句子的意思是：山坡被滑雪者使用的越多，雪崩就越可能发生。 、
11.D尽管选项A、B和D都能和continuous搭配，从全段的内容判断，只有process是最佳选择，因为该段描写的是如何防备雪崩，及如何做好安全措施等一系列问题。
12.A选项A、B、c都可以与weather搭配，但是根据上下文，只有A最为符合文章的内容。
13.B选项A不符合句子的意思;c不能和risk搭配;D也不符合句子的意思，因为不可能完全消除雪崩的隐患。
14.C该句主句使用的是被动语态，第二个动词是pay attention t0的被动形式。l选项A、B、D均不符合句子的意思。
15.A该句是作者给出的一系列忠告之一，即，认真观察地形，注意明显的雪崩路径：没有植物或植物被毁坏的地方。选项8、C、D均不符合句义。
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