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　　Death comes quickly in the mountains．Each winter holidaymakers are caught unawares as they happily ski away from the fixed runs, little realizing that a small avalanche can send them crashing in a bone-breaking fall down the slope and leave them buried under tons of crisp white snow．There are lots of theories about how to avoid disaster when hit by an avalanche．Practice is normally less cheerful．

　　The snow in the Salzburg of Austria where a recent disaster took place was typical avalanche material．For several days before the incident I had skied locally．Early winter snow was wearing thin and covered with ice．On top of that new, warmer flakes were gently falling to produce a dangerous carpet．To the skier who enjoys unmarked slopes it is tempting stuff, deep new power snow on a hard base-the skiing that dreams are made of．And sometimes nightmares．

　　Snow falls in sections like a cake．Different sections have different densities because of the temperatures at the time of the fall and in the weeks afterwards．Problems come when any particular section is too thick and not sticking to the section beneath．The snow of the past few weeks had been falling in rather higher temperatures than those of December and early January．The result of these conditions is that even a slight increase in the temperatures sends a thin stream of water between the new snow and the old．Then the new snow simply slides off the mountain．

　　Such slides are not unexpected．Local citizens know the slopes which tend to avalanche and the weather in which such slides are likely．Traps are set to catch the snow or prevent it slipping; bombs are placed and exploded from time to time to set off small avalanches before a big one has time to build up; and above all, skiers are warned not to ski in danger areas．

　　In spite of this, avalanches happen in unexpected areas and, of course, skier ignore the warnings．The one comfort to recreational skiers, however, is that avalanche incidents on the marked ski slopes are quite rare．No ski resort wants the image of being a death trap．

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　　When I was in the 8th grade in Ohio, a girl named Helen in my class had a terrible accident．As she was running to the bus in order not to 　　1　　 it, she slipped on some ice and fell 　　2　　 the rear wheels of the bus．She 　　3　　 the accident, but was paralyzed(残疾)from the waist down．I went to see her, in my 13-year-old 　　4　　 thinking she wouldn't 　　5　　 normally from then on．

　　Over the years, I 　　6　　 and didn't think much about Helen after that．Three years ago, in Florida, my oldest son was 　　7　　 by a car while riding his bike, causing a 　　8　　 brain injury．While I was looking after my son, a lady who said she was the hospital's 　　9　　 worker called．

　　A short time later, a beautiful woman, in a wheelchair, 　　10　　 into my son's room with a box of tissues．After 16 years, I 　　11　　 recognized Helen．She smiled, handed me the tissues and hugged me．I told her who I was, and after we both 　　12　　 the shock of that, she began to tell me about her life 　　13　　 we last saw each other．She had married, had children and gotten her degree 　　14　　 she could smooth the path for those less 　　15　　 than her．She told me that if there was anything she could give me, it would be 　　16　　．

　　Looking at this wonderful, giving person, I felt 　　17　　．But I also felt the 　　18　　 hope I had felt since learning that my son was hurt．From this person that I thought would have no 　　19　　 of life, I learned that where there is life, there is hope．My son miraculously(不可思议地)recovered and we moved back north, but I owe Helen a 　　20　　 that I can never repay．

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