阅读下面的短文，根据内容，从每题的四个选项中选择最佳的一项。 Mark Twain(马克·吐温) was an American writer. One day he went to a city by train. He wanted to see one of his friends there. Mark Twain was a very busy man. He usually forgot something. When he was in the train, the conductor asked him for his ticket. Mark Twain looked for the ticket here a nd there, but he couldn't find it. The conductor knew Mark Twain. She said, 'show me your ticket on your way back .And if you can't find it, it doesn't matter.' 'Oh, but it does,' said Mark Twain.?'I must find the ticket .If I can't find it, how can I know where I'm going?' 1. Mark Twain was a ________. [     ] A. teacher B. student C. doctor D. writer 2. Mark Twain went to the city to _____________. [     ] A. see his friend B. buy some paper C. sell his books D. see his parents 3. When he was in the train, the conductor asked him for _________. [     ] A. some books B. the ticket C. a pen D. some food 4. Mrak Twain didn't show his ticket because he couldn't ______it. [     ] A. buy B. find C. look for D. know