听力原文：W: Hey, Mike! Did you attend Mr. Johnson's seminar on the History of Chicago? M: Yes, I did. I didn't notice you were there, too. W: I was late for it. Wasn't it a great seminar? I have learned so much! M: It certainly was. I hadn't understood that Chicago was such a young city, less than 200 years old. W: Yes, I thought it was an old city before, but it turned out that I was wrong. You still remember what Mr. Johnson said? The army fort, Fort Dearborn, was built in 1803 in the place that would become Chicago. Chicago didn't officially become a town until 30 years later, in 1833. M: Yes, and when it officially became a town in 1833, it was very small. It had a population of only 350. Think about that, only 350 people! It was really a tiny town by then. W: But it's a pity that after Chicago had grown, much of it was destroyed in a fire. Just imagine! What a big fire it was! M: The Great Chicago Fire was in 1871. Chicago wasn't even forty years old at the time, but it had grown much bigger. W: Yet only twenty-two years later, in 1893, Chicago was able to host a World's Fair. It was such a huge development for a city. M: Yes. Chicago had been rebuilt after the fire and was eager to show itself off to the rest of the world at the World's Fair in 1893. W: I will attend another seminar on the Economy of Chicago next week. Mr. Johnson will talk about the economy specifically. Will you be there too? M: Yes, so I will see you next Thursday. (23)