Today we're going to discuss the history of the bicycle. Although many people attribute its invention to the 19th century, the first two-wheeled vehicle appeared in 1817, invented by Karl Drais. It was called a 'running machine' because riders pushed their feet against the ground. Later, in the 1860s, pedals were added to the front wheel, leading to the penny-farthing. However, this design was unsafe due to its high center of gravity. The modern safety bicycle, with two equal-sized wheels and a chain drive, emerged in the 1880s and became widely popular, especially among women who gained new mobility.
❓ 前轮大后轮小的自行车（Penny-farthing）存在的一个主要问题是什么？
A. A. 它没有踏板。
B. B. 太慢了。
C. C. 由于重心过高，它很危险。
D. D. 生产成本过高。
✅ 正确答案
C. It was dangerous because of its high center of gravity.