Please answer the following question: Andrew Ritchie, inventor of the Brompton folding bicycle, once said that the perfect portable bike would be "like a magic carpet...You could fold it up and put it into your pocket or handbag". Then he paused: "But you'll always be limited by the size of the wheels. And so far no one has invented a folding wheel." It was a rare -- indeed unique -- occasion when I was able to put Ritchie right. A 19th-century inventor, William Henry James Grout, did in fact design a folding wheel. His bike, predictably named the Grout Portable, had a frame that split into two and a larger wheel that could be separated into four pieces. All the bits fitted into Grout's Wonderful Bag, a leather case. Grout's aim: to solve the problems of carrying a bike on a train. Now doesn't that sound familiar? Grout intended to find a way of making a bike small enough for train travel: his bike was a huge beast. And importantly, the design of early bicycles gave him an advantage: in Grout's day, tyres were solid, which made the business of splitting a wheel into four separate parts relatively simple. You couldn't do the same with a wheel fitted with a one-piece inflated tyre. So, in a 21st-century context, is the idea of the folding wheel dead? It is not. A British design engineer, Duncan Fitzsimons, has developed a wheel that can be squashed into something like a slender ellipse . Throughout, the tyre remains inflated. Will the young Fitzsimons's folding wheel make it into production? I haven't the foggiest idea. But his inventiveness shows two things. First, people have been saying for more than a century that bike design has reached its limit, except for gradual advances. It's as silly a concept now as it was 100 years ago: there's plenty still to go for. Second, it is in the field of folding bikes that we are seeing the most interesting inventions. You can buy a folding bike for less than PS1,000 that can be knocked down so small that it can be carried on a plane -- minus wheels, of course -- as hand baggage. Folding wheels would make... Which of the following would be the best title for the text? A) Three folding bike inventors B) The making of a folding bike C) Progress in folding bike design D) Ways of separating a bike wheel
A:
C