In the eighteenth century, cities became larger and larger. People moved from the countrys

ide and small towns to the cities because there were more for them to do in the cities.

On Sundays and holidays, they liked to leave the cities and have a good time in the countryside. But not every family had a horse and wagon. People wanted and needed another form. of transportation. Inventors in many countries fried to meet this need.

The first bicycle, which was very simple, appeared in 1790. People called it "the horse on wheels" .Then in 1861, with many improvements, bicycles became a practical form. of transportation.

People liked hikes because they weren't as expensive as horses. They didn't need to build a special house to keep them in, and they didn't have to feed them. They could ride them in the city and in the countryside. Everybody in the family could ride—men and women, girls and boys.

The main idea of this passage is ______.

A．the bicycle has become a practical form. of transportation

B．transportation has changed through time

C．travelling in the countryside is difficult

D．bicycle travel is easy in the city