Good morning. Today we're going to discuss the history of the bicycle. In the early 19th century, the first two-wheeled vehicle, called the 'draisine', was invented by Karl Drais. It had no pedals; riders pushed their feet against the ground. Later, in the 1860s, pedals were added to the front wheel, creating the 'velocipede'. However, this design was uncomfortable and difficult to ride. It wasn't until the 1880s that the 'safety bicycle' with a chain drive and equal-sized wheels became popular, which is similar to modern bicycles. This design was safer and faster, leading to a cycling boom.
❓ Đặc điểm chính nào của 'xe đạp an toàn' đã khiến nó trở nên phổ biến?
A. Nó không có bàn đạp và người điều khiển dùng chân để đẩy.
B. Nó có bộ truyền động xích và các bánh xe có kích thước bằng nhau.