[2014·济南调研]用0,1,2,3,4,5六个数字组成无重复数字的四位数，若把每位数字比其左邻的数字小的数叫做“渐降数”，则上述四位数中“渐降数”的个数为( )
A．14
B．15
C．16
D．17
答案：B
由已知可知，只需找出组成“渐降数”的四个数字即可，等价于六个数字中去掉两个不同的数字．
从前向后先取0有0与1,0与2,0与3,0与4,0与5，共5种情况；
再取1有1与2,1与3,1与4,1与5，共4种情况；
依次向后分别有3,2,1种情况．
因此，共有1＋2＋3＋4＋5＝15(个)“渐降数”．
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| "You will never walk again. You will have to use a wheelchair." I heard his 1 fall heavily on my ears, numbing my soul. If I had never felt hopeless before, I felt hopeless then. The car accident has left me unconscious. When 2 , I found both legs in casts (石膏). While I had other serious injuries, my 3 were my first concern. Working as a special needs teacher and busy and active by nature, I couldn't imagine being 4 in a wheelchair. Lying in my bed, I wondered how I 5 give my ten-year-old son hope that mom would 6 . He'd been cheerful on every visit, but I saw 7 in his eyes. He needed the ray of hope that I would not be in a wheelchair forever.Just maybe, I thought, I could use this experience to teach him what to do when misfortune 8 . It didn't take me long to become 9 with my limited movements and even with the pace the doctors were willing to go with me. I was determined to learn everything they showed me. Every night in my private room, as soon as I knew I wouldn't be 10 or discovered, I would move myself from the bed to the floor, 11 on to the bed rail (床栏杆) for life, and slowly putting my weight 12 my feet.After several weeks of such difficult 13 , my strength and confidence continued to 14 . It came the time to share my accomplishments with the person most 15 to me.One night, when I heard my son greet the nurses at the station, I 16 myself up.As he opened the door, I took a few small steps. 17 , he could only watch as I turned and started back to bed.All of the pain, the fear, and the struggle 18 as I heard the words I had longed to hear,"Mommy, you can walk!" I am now able to walk alone, sometimes using a stick.I am able to take public transportation to shop and visit friends.My life has been blessed with many 19 of which I am proud.But none has ever brought me the satisfaction and joy 20 by those four little words of my son. | ||||
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