Good morning, everyone. Today, we're going to discuss the history of the bicycle. As you know, the first bicycle, called the 'draisine', was invented in 1817 by a German baron. It had no pedals; riders pushed their feet against the ground. Then, in the 1860s, pedals were added to the front wheel, creating the 'velocipede'. However, this design was uncomfortable because of its rigid frame and iron wheels. It wasn't until 1885 that the 'safety bicycle' was introduced, featuring a chain drive and two equal-sized wheels, which made cycling much safer and more popular. So, the key innovation of the safety bicycle was...
❓ 讲座中提到的安全自行车的主要改进是什么?
A. 它在前轮上加装了踏板。
B. 它有两个大小相同的轮子和链条传动装置。
C. 它由更轻的材料制成。
D. 它的座椅更舒适。
✅ 正确答案
It had two wheels of equal size and a chain drive.