文档介绍：完型填空
Bill was a very good pilot(飞行员).   He had been in the air force for several years,   and had been very essful.   Now he was sent to a small field in the middle of a forest,     1   planes were able to attack(进攻) the enemy very easily,     2   it was near the front line,   but   3   to find.   The forest trees were very tall and very   4   on all sides,   so planes had to go down very quickly and then stop their falling very   5   before they   6   the ground.   Only the   7   pilots were able to land safely,   and even some of those lost their planes and   8   because they hit the tress on the ground. 
 After Bill had arrived,   he was not   9  until he was able to fly closer to the trees than any of   10   pilots,   and soon all the pilots who used that field were trying to   11   each other at flying   12   over the forest.   Every time one of their planes came back form the attack on the enemy,   the other pilots used to run   13   and watch,   to see how near the trees   14   pilot took it,   if the eeded in taking very near,   they laughed and shouted. 
 Bill soon   15   exactly how near he was able to go safely,   and then one day he flew so close to the   16   of the trees that some of the branches   17   the bottom of his plane.   The other men in the plane seemed rather   18  ,   but Bill only laughed as he landed the plane without any   19   in the middle of