抛物线y=2x2+bx+8的顶点在x轴上，则b=（ ）。

                                                              Joy in the Journey
     If you have ever been discouraged because of failure, please read on. For often, achieving what you
set out to do is not the important thing. Let me   1   .
     Two brothers decided to  2   a deep hole behind their house. As they were working, a couple of older boys stopped by to   3   .
     "What are you doing?" asked one of the visitors.
     "We plan to dig a hole all the way through the  4   !" one of the brothers volunteered   5   .
     The older boys began to  6  , telling the younger ones that digging a hole all the way through the earth
was  7   . After a long silence, one of the   8    picked up a jar full of spiders,   9   and many other kinds
of insects. He   10   the lid and showed the wonderful   11  to the scoffing (嘲笑的) visitors. Then he
said quietly and confidently, "Even if we don't dig all the way through the earth, look at what we have
found   12   the way!"
     Their goal was far too ambitious, but it did cause them to dig. And that is    13  a goal is for - to cause
us to move in the direction we have chosen,   14   , to set us digging!
     But not every goal will be fully   15   . Not every job will end   16  . Not every hope will come to pass. Not every love will last. Not every dream will be   17   . But when you fall short of your aim, perhaps you can say, "Yes,   18    look at what I've found along the way! Look at the wonderful things   19  my life
because I tried to do something!" It is in the digging that life is lived. And I believe it is the joy in the
journey, in the end, that truly  20   .