A、Because it has plastic wheels. B、Because it has plastic tires. C、Because it has a plastic frame. D、Because it has no metal par

In England bicycles are often called "boneshakers" because they shake your bones! But now there’s a new smooth bicycle on the market: it’s made of plastic and it comes from Sweden.
   A lot of different people worked on the development of this new bicycle; the original idea came from an engineer in Sweden, and he asked for help from America as well as from a British firm.
   Together they solved all the problems. First, they had to invent a new kind of plastic; then they had to design a new shape; and finally they had to produce metal parts which fit properly into the plastic frame. The result is a complete success.
   Because it has a plastic frame, it is more flexible than the ordinary metal bike. This means that it’s more comfortable to ride, and quieter as well. You feel more comfortable as you ride on the road. And of course it won’t rust.
   It never needs oil at the center of the wheels; and it’s quite strong, so it won’t break if you crash it! The plastic is very hard so it won’t be damaged by sunshine or cigarette burns.