Jeff Keith has only one leg. When he was only twelve years old, Jeff had cancer. Doctors had to　16　 off most of his right leg.
　17　 Jeff puts on an artificial leg(假肢). The leg is plastic. With the plastic leg, Jeff can ski, ride a bicycle, swim, and play soccer. He can also run.
Jeff made a plan with his friends who had plastic legs, 　18　. They decided to 　19　 across America. They all wore special T-shirts.　20　 it was “Run, Jeff, Run, Jeff Keith’s Run Across America”.
Jeff Keith ran across the United States from the east to the west 　21　 he was twenty-two years old. He started running in Boston(波士顿). Seven　22　 later, he stopped　23　 in Los Angeles（洛杉矶）. He ran 3,200 miles (1 mile =" 1.6093km)." Jeff wore out thirty-six pairs　24　 running shoes and five plastic legs. Jeff　25　 in cities on the way to Los Angeles. In every city people gave Jeff money. The money was not for Jeff,　26　 for the American Cancer Society. The Society used the money to help people know 　27　 about cancer.
On the way to Los Angeles, Jeff talked to people about　28　. Jeff is disabled, but he can do many things. He finished college and is studying to be a lawyer(律师). Jeff says, “People can do　29　 they want to do. I want people to know that. I ran　30 for disabled people. I ran for everybody.”

As everyone knows, there are many 　16　 of transportation in the world, like bicycles, buses, ships, trains and 　17　 .
If you are in big  18　like Shanghai or Beijing, maybe you get to school   19  a subway or you have to 　20　 to school because you live in a mountain village. Here I am just trying to say something about　21　 .
Ten years　22　, bicycles were very　23　in most villages.  24　 family had one or two of bicycles. Children got to school by bicycle; 　25　 rode bicycles to go shopping. Then motorcycles (摩托车)   26  to become popular. People no longer rode bicycles because motorcycles ran   27  faster.  But now, in some countries，bicycles are highly suggested
  28  the main means of transportation. They think buses, cars and motorcycles pollute(污染) the air but bicycles   29  . So, to live a low-carbon life,   30  a bike is a good way.