美国临床实验室标准委员会曾制定“保健的质量体系模式”，自下而上分为5层，其中最基础的

     Years ago in Scotland, the Clark family had a dream. Clark and his wife worked and   1   , making
plans for their nine children and themselves to travel to    2  . It had taken years, and they had   3    saved
enough money and had got passports (护照) and    4   for the whole family to the United States.
     The entire family was filled with   5   about their new life.    6   , seven days before their departure, the
youngest son was bitten by a dog. The doctor sewed up the boy but he   7   a yellow sheet on the
Clarks' front door.   8   the possibility of rabies (狂犬病), they should be quarantined (隔离) for
fourteen days.
     The family's   9   was destroyed. They would not be able to make the trip to America as they had 
  10  . The father, filled with disappointment and   11   , hurried to the dock to watch the ship leave-without
the Clark family.   12   of disappointment came to the father. Five days    13   , the tragic news spread
throughout Scotland - the mighty Titanic had sunk. The unsinkable ship had sunk,   14   many lives with
it. The Clark family should have been on that ship,   15   because the son had been bitten by the dog,
they were   16   in Scotland. When Mr. Clark heard the news, he    17  his son and thanked him for saving
the family. He thanked God for saving their lives and turning   18   he had felt was a(n)   19   into a
blessing.
     Although we may not always understand, all things    20   for a reason.