Good morning, class. Today we're going to discuss the history of the bicycle. Now, many people assume the bicycle was invented in the 19th century, and that's partly true. The first two-wheeled vehicle, called a draisine, appeared in 1817, but it had no pedals. It was essentially a wooden frame with two wheels, and riders pushed themselves along with their feet. The real breakthrough came in the 1860s when pedals were attached to the front wheel. However, these early bicycles were very difficult to ride because the front wheel was large, making them unstable. It wasn't until the 1880s that the chain drive was introduced, which allowed the rear wheel to be powered, creating a much safer and more efficient design. This design, known as the safety bicycle, quickly became popular and is the basis for modern bicycles.
❓ 根据讲座内容,前轮装有脚踏板的自行车主要问题是什么?
A. A. 它们太重了,搬不动。
B. B. 由于不稳定,它们很难骑乘。
C. C. 他们没有刹车。
D. D. 它们生产成本过高。
✅ 正确答案
B. They were difficult to ride due to instability.