[不定项选择题]共用题干 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 _________(51)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 un-
stable for the slope. __________(52)supports it.Determining the critical load,the amount of over-burden
which is
______ (53)to cause an avalanche,_________(54)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________(55)
of avalanche.Snow does not ________ (56)significantly on steep slopes;also,snow does not
__________(57)easily on flat slopes.Human-triggered avalanches have the greatest incidence when the
snow'S angle of rest is_________(58)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_________(59)
enough to hold snow but steep enough to ski has the potential to generate an avalanche,regardless of the an-
gle.Additionally,avalanche risk increases with__________(60);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__________(61),including route selection and examination of the
snowpack,weather___________(62),and human factors.Several well-known good habits can also
__________ (63)the risk.If local authorities issue avalanche risk reports,they should be considered and all
warnings should be paid__________(64)to.Never follow in the tracks of others without your own evalua-
tions;snow conditions are almost certain to have changed since they were made.Observe the terrain and note
obvious avalanche paths where plants are_________(65)or damaged.Avoid traveling below others who
might trigger an avalanche. _________(60)
A.use
B.time
C.snow
D.rain