Jumping on your bike, even in the city, is becoming increasingly popular--- in London, for example, cycle use has more than doubled in the past ten years. So, which is the best bike for you?     If you're traveling to work, a folding bike such as one of the models here is suitable unless you're cycling more than a couple of miles, in which case it might be uncomfortable . You can take a fold-up on the train and as it goes indoors with you, it's secure .     For longer journeys, a road bike with drop handlebars and narrow tyres is a good choice. Try Specialized, from PS400. Note that the riding position encourages you to look downwards, which can be dangerous.     Mountain bikes are best suited to off-road travel; their fat and strong tyres are good for climbing steep, muddy slopes . Good brands include Trek and Giant, with prices starting at less than PS300.     A hybrid bike (halfway between a mountain bike and a road bike) is a good compromise with more upright riding position and thin, fast tyres. Ridgeback makes great hybrids, from around PS350.     For a classic sit-up-and-beg bike, it's still hard to beat Pashley, which makes its bikes by hand. Expect to pay around PS500.     Once you've picked your bike, sizing is crucial or you may suffer back or neck pain. A famous bike shop will help you choose the right size frame. The height of the seat should be adjusted carefully---again, a good shop will advise. If you only plan to cycle once or twice a month, you can choose a lower-priced bike, but for regular use, paying more means better quality: cheaper bikes need more frequent adjustment of brakes and gears   ---and tend to be heavier, too. Finally, items such as mudguards  aren't always included. The main purpose of this passage is to   _  .
give advice on how to choose a bike advertise some famous bike brands encourage people to go to work by bike introduce the advantages of different bikes