answer: #Person1# is planning to buy a bicycle and asks #Person2# for some advice. #Person2# asks the reasons and explains the difference between a mountain bike and a road bike.
documents: #Person1#: I'm planning to buy a bicycle. As you are quite a cycling enthusiast, I wish you might give me some advice. 
  #Person2#: With pleasure, chap. But before I start, I need to know what you want a bike for? 
  #Person1#: My purposes are two-fold. On the one hand, I've grown bored of commuting on suffocating buses every day and decided to ride to work. On the other hand, bicycling is a sport, and I intend to build up my body through constantly taking a ride over the weekends. 
  #Person2#: Cycling during weekends? Do you me riding on the mountainous countryside orjust the neighboring towns? 
  #Person1#: Does that make any difference? 
  #Person2#: Can't be greater. If you ride on bumpy, hilly roads, a mountain bike is what you need. But if you just ride comfortably along the city lanes, you might choose a road bike. 
  #Person1#: Are they designed differently? 
  #Person2#: A road bike features skinny tires and a light-weight frame. Its riding position puts you bent over the handlebars. It's not particularly beefy in construction, and generally, it won't stand up well under heavy loads or on really rough surfaces. In contrast, mountain bikes have wide tires and a stout frame. You sit higher on them and don't have to hunched over.