He found all of them had already been taken except for_ 空格中填什么单词合适?

one
来自阅读理
A Soldier's Brilliant Idea
Mr.Robinson had to travel somewhere on business,and as he was in a hurry,he decided to go by air.He liked sitting beside a window when he was flying,so when he got on to the plane,he looked for a window seat.He found all of them had already had been taken except for one.There was a soldier sitting in the seat beside this one,and Mr.Robinson was surprised that he had not taken the one by the window; but,anyhow,he at once went towards it.
When he reached it,however,he saw that there was a notice on it.It was written in ink and said,"This seat is preserved for proper load balance,thank you." Mr Robinson had never seen such an unusual notice in a plane before,but he thought that the plane must be carrying something particularly heavy in it,so he walked on and found another empty seat,not beside a window,to sit in.
Two or three people tried to sit in the window seat beside the soldier,but they too read the notice and went on,when the plane was nearly full,a very beautiful girl hurried into the plane.The soldier,who was watching the passengers coming in,quickly took the notice off the seat beside himself and in this way succeededin having the company of the girl during the whole trip.
英语幽默：士兵坐飞机有美女陪伴的高招
由于生意方面的事,罗宾逊先生得出趟门.因为有点紧急,他决定坐飞机.乘机旅行时,他喜欢靠窗坐,故而一登机,他就寻找一个靠窗的座位.他发现只有一个靠窗的座位还空着.在那空座位边坐着一名士兵.令罗宾逊先生纳闷的是,这位士兵没有坐靠窗的位置.罗宾逊先生不管那些,他马上径直朝那个空座位走去.
然而,等到了那儿,他看见座位上有则启事,是用钢笔写的：“为保持装载平衡,特预设该位置,”罗宾逊先生还从来没有在飞机上见过如此不同寻常的启事.不过,他想飞机上一定装了什么特别重的物品,于是他找了个不靠窗的位置.
又有两三个乘客试图坐在那个士兵旁的靠窗座位上,他们看到那则启事就走开了.当快满座时,一位非常美丽的姑娘匆匆走进机舱.一直在注意进舱旅客的那个士兵赶紧拿掉他旁边空座位上的启事.士兵用这种办法,成功地找到了一位姑娘一路作伴.