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...
❓ Bài giảng đã đề cập đến cải tiến chính của xe đạp an toàn là gì?
A. Nó đã thêm bàn đạp vào bánh trước.
B. Nó có hai bánh xe cùng kích thước và bộ truyền động xích.
C. Nó được làm từ những vật liệu nhẹ hơn.
D. Nó có một chiếc ghế thoải mái hơn.
✅ 正确答案
It had two wheels of equal size and a chain drive.