The young engineer sat down on a rock and rested his head in his hands. He would never get home; it was   1   . For weeks he had been   2   in the Northwest Canadian forest. Now there was a terrible   3   behind his eyes, and worse of ail, he had gone   4  .

    Suddenly a man   5   out of the woods, an Indian who had been hunting in the area. Seeing the engineer's   6  , he caught a fish in a nearby   7   and fed the sick man the   8   of the fish and some flesh from its head.   9   within a few hours the engineer's pain was   10   . A day later he could   11  again, and the next day he had   12   recovered.

    When he returned home, the engineer told the   13   to Dr Price. Not until years later did it become a(n)   14   fact that this was just an everyday   15   doing its work. For what the engineer did, by eating fish eyes, was to   16  his vitamin (维生素).

    Vitamin A's biggest job is to keep the eyes   17   . Without A, people and animals get night blindness and other eye problems. Without A, people can even be totally blind.  A helps to keep the skin in good   18  . A also helps   19  with bones and teeth and has to do with proper   20   of blood cells.

        KEY: 1-5 AACAB  6-10 DADBB  11-15 ABDBC  16-20 DDCAA