阅读下面短文,然后从短文后各题所给的A、B、C、D四个选项中,选出可以填入空白处的最佳选项。
In the eighteenth century, cities became larger and larger. People moved from the countryside to the cities because there was 1 work for them to do in the cities.
On Sundays and during holidays, they liked to 2 the cities and have a good time in the countryside, but not every 3 had a horse. People needed another kind of transportation. Inventors in many countries tried 4 this problem.
The first documented bicycle was invented by a German, Baron Von Drais, in the 1810s. It was a walking machine made 5 wood. People pushed their 6 against the ground to move forward. It 7 people to get around parks and gardens.
In 1865, pedals(踏板) were added to the front wheel. But when people 8 it on stones, they shook a lot.
In 1870, the first all-metal bicycle 9 rubber tyres(橡胶轮胎) was invented. But the two wheels were not the same 10. The front wheel was much larger than the back one. This machine was the first to 11 bicycle. However, it was hard to ride and it was very 12.
In the 1890s, chain drive, the pneumatic(充气的) tyre and same-sized wheels made the ride 13 and more comfortable. People loved it 14 it helped them enjoy more free time.
Bicycling became 15, not just with men but also with women.