Two strangers were sitting together in a plane . They were on a long journey . One of the men was a teacher . The other was a farmer . They sat without talking for a while , then the farmer said , " Let's do something to pass the time ." " What do you want to do ?" the teacher asked . " We can ask each other riddles ( )," the farmer said, " You start." " Let's make the rules first ," the teacher said . " And to make the game more interesting , let's play it for money . If we don't know the answer to the riddle , we have to pay a dollar ." The farmer thought about this for a while , then he said , " That's not fair( . You are a teacher , an educated ( ) man . You know more things than I do . I am just a farmer ." " That's true ," the teacher said , " What do you think we should do ?" The farmer said , " If you don't know the answer to a riddle ,you pay me 100 dollars .If I don't know the answer to the riddle , I'll pay you 50 dollars." The teacher thought for a while , then he said , " OK. That's fair . Who'll go first ?" "I will ," the farmer said . " Here's my riddle . What has three legs when it walks , but only two legs when it flies ?" The teacher thought and thought , " What has three legs when it walks, but only two when it flies ?" Then he said , " That's a good one . I don't know the answer ." He gave the farmer 100 dollars and said , " Tell me the answer . What is it ?" " I don't know , either ." The farmer said , and gave him 50 dollars . The farmer wanted to   _   .
make the journey interesting . see if the teacher was lucky know if the teacher was clever . make friends with the teacher .