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The history of the bicycle goes back more than 200 years. In 1791，Count de Sivrac ________onlookers in a park in Paris as he showed off his two-wheeled invention ，a machine called the celerifer. It was basically an ________version of a childrens toy which had been in ________ for many years. Sivracs celerifer had a wooden frame，made in the ________ of a horse ，which was mounted on a wheel at either end. To ride it ，you sat on a small seat ，just like a modem bicycle ，and pushed ________ against the ________ with your legsthere were no pedals. It was impossible to steer a celerifer and it had no brakes，but despite these problems the invention very much ________to the fashionable young men of Paris. Soon they were ________ races up and down the streets. Minor ________were common as riders attempted a final burst of ________ . Controlling the machine was difficult ，as the only way to change ________ was to pull up the front of the celerifer and ________it round while the front wheel was ________ in the air. Celerifers were not popular for long ，however ，as the ________of no springs ，no steering and rough roads made riding them very uncomfortable. Even so，the wooden celerifer was the ________of the modem bicycle. 词汇： count / kaunt / n. 伯爵 brake / breik / n. 闸，刹车 onlooker /n,luk / n. 观众 burst / b :st / v. 爆发，突发，爆炸 | 
