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...
❓ ¿Cuál fue la principal mejora de la bicicleta de seguridad mencionada en la conferencia?
A. Añadió pedales a la rueda delantera.
B. Tenía dos ruedas de igual tamaño y una transmisión por cadena.
C. Estaba hecho de materiales más ligeros.
D. Tenía un asiento más cómodo.
✅ 正确答案
It had two wheels of equal size and a chain drive.