An avalanche is a sudden and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches 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 it. Determining 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 low 5 of avalanche. Snow does not 6 significantly on steep slopes; also, snow does not 7 easily on fiat slopes. Human-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 degrees. The 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 angle. Additionally3, 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% safe. Good avalanche safety is a continuous 11 , including route selection and examination to the snowpack, weather 12 , and human factors. Several well-known good habits can also 13 the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings should be paid 14 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 15 or damaged. Avoid 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:
1.angle of rest：这里指积雪保持静止的角度。
2.rule of.thumb：指“a broadly accurate principle，based on experience or practice rather that theory”，即“通用法则，经验法则”。
3.Additionally：是一个副词，用来引人新的事实或论点，意为“此外”。
4.backcountry：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 ski。flat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。
Taking a Nap During the Day
Medical experts say most Americans do not get 1 sleep. They say more Americans need to rest for a short period in the middle of the day. They are advising people to sleep lightly before 2 with other activities.
One study earlier this year found that persons who sleep for a few minutes during the day were less 3 to die of disease. The study followed more than 2,300 Greek adults 4 about six years. Adult who rested for half an hour 5 three times a week had a 37 percent lower risk of dying from heart disease than those who did not nap.
Study organizers said the strongest evidence was in working men. They said naps might improve 6 by mitigating tension caused by work.
Some European and Latin American businesses have supported the 7 of napping for many years. They urge people to 8 work, go home and have a nap before returning. In the United States, some companies let workers rest briefly in their offices. They believe this reduces in their offices. They believe this reduces 9 and accidents, and 10 increases the amount of work a person can do.
Sleep experts say it is likely that people make more mistakes at work than at other times1. They say people should not carry out important duties when they feel 11 . And they say the best thing to do is to take a nap. About twenty minutes of rest is 12 you need. Experts say this provides extra energy and can increase your effectiveness 13 the end of the day. But experts warn that a nap 14 last no more than twenty to thirty minutes. A longer nap will put the body into deep sleep2 and waking up3 will be 15
词汇:
Nap n. 打盹 mitigate v.减价
urge v.催促，劝告
注释:
1.people make more mistakes at work than at other times：人们在工作(时间)中出错的概率比其它的时间要多。本句中的at work可以理解为during their work time。
2.put…into deep sleep：使……进人深睡状态
3.waking up：从上下文判断，waking up是“自己醒过来”的意思，不是“唤醒”。
练习:
1. A sweet B sound C bad D enough
2. A checking B sharing C continuing D meeting
3. A lovely B likely C fondly D finely
4. A for B at C in D with
5. A at least B at most C at last D at first
6. A ability B health C thinking D life
7. A experiment B reform C idea D way
8. A repeat B improve C change D leave
9. A work B mistakes C energy D time
10. A never B seldom C too D also
11. A ready B good C sleepy D awake
12. A all B few C any D nothing
13. A unless B while C until D during
14. A would B may C might D should
15. A helpful B difficult C easy D happy
答案与题解:
1.D本段第二句说“more Americans need to rest for a short period in the middle of the day”。引导我们选择(not)enough。因为睡眠不够，才要中午“打个盹”。选项A：文不对题。选项B：bad(sleep)与上下文不符，因为通篇文章没有提到过，中午打盹的原因是晚上没有睡好。选项C：明显不合乎逻辑。“由于没有睡不好(即：晚上睡好了)，白天还要补睡一会儿”，于理说不通。所以，惟一合理的选择是enough。 ’
2.C空格2所在句子的意思是：医学专家建议人们在进行其它活动之前，小睡一会。四个选项中，只有continuing(选项C)最接近上述的理解。
3.B空格3所在的句子说的是“心脏病致死”的问题，lovely，fondly和finely分别表达“可爱”、“喜欢”和“美好”的意思，明显不对。less likely是“可能性较低一些”的意思，选择likely符合上下文的意思。本段最后一句说，成年人白天打盹半小时，一周三次，其心脏病致死的概率比不打盹的人要低37%。这更证实了选likely是正确的。
4.A本句的意思是，调查进行了六年。about six years之前要用表达一段时间的介词for。介词at和with明显与about six years不搭配，而选项in(about six years)表达的是未来的时间，如：He will come to Beijing in one day or tw0.(他一、两天之内会到北京。)
5.A at first和at last明显与本句的意思不符。若选at most(最多)，本句的意思成了“成年人白天打盹半小时，一周不得超过三次，其心脏病致死的概率比不打盹的人要低37%”，意思有点令人费解。改说成，“一周至少三次”才说得通。所以at least是答案。
6.B通篇文章在阐述白天打盹有益于健康，选项B是答案。
7.C空格7所在的句子的意思是：多年来，欧洲和拉丁美洲的一些公司支持白天打盹的 ? (空格中填哪一个词?)。很明显，空格中填入experiment(试验)或reform(改革)则离题太远，而way(方式)肯定没有idea(想法)好。C是答案。
8.D从上下文判断，空格8的词应该与“中止(work)”有关。四个选项中，只有leave合乎这一条件。而其它三个选项repeat(重复)、improve(改进)和change(改变)与后半句的go home and have a nap搭不上。
9.B前面一句说，美国有些公司让职员在办公室打个盹，这样可以减少些事故等。填人空格9的词应该与accidents(事故)一样，是一个负面意思的词。mistakes(选项B)符合这个条件，是答案。reduce work/energy time都不合理。
