根据首字母提示完成所缺单词
One day,the American w_____ Mark Twin went to a city b（y） train.He wanted to see a friend of h（is）.He was a very busy man and he often f_____ something.
When he was in the train,the conductor asked him to show his t（icket）.Mark Twin looked for it here and there,but he c（ouldn’t） find it.The conductor k_____ him.So she said,“S（how） me your ticket on your way b_____ home.And if you can’t find it,it doesn’t matter.” “Oh,but it does.” said Mark Twin,“I must find it.If I can’t find it,how can I know w（here） I’m going?”