taking part 是分词短语作后置定语的.这时它的逻辑主语就是它所修饰的 the oldest car
而 the oldest car 和 take part 是主动关系,所以用现在分词,表主动,进行.
它等于 that was taking part.(定语从句）it sped downhill at the end of the race and its driver had a lot of trouble trying to stop it.try为啥要加ing?这是个固定句型have trouble in doing sth干什么事有困难in可以省