某进口公司持有美元，但要求对外支付的货币是日元，可以通过（），卖出美元，买人日元，满

      There are different kinds of trains in the world. Trains can       1       people, animals, and other things.
Some trains are      2     , the others are slow. They can reach most of the cities and towns. Some trains go
    3    the hills if they are too high to go over. In big cities, the streets are usually     4     and some cars and
buses often have to wait.
      So you can find trains under the      5       and trains on a rail above the streets. People can quickly be
brought in or taken out. Can a train run over       6     ? Yes, it can.  There are many bridges over the
rivers.  But it is not easy to      7       bridges. Today's trains have dining-rooms for people. You
may      8     something in them on the way if you are hungry. Trains are      9      to men, women and
children. Many children like to play with model trains. With the model trains they can build their own rails
and      10       thewonderful world of trains.