Exercise 1: sample answer

It lacked pedals and cranks, a chain, a proper brake, air-filled tyres and a comfortable seat and frame: it was a heavy wooden machine pushed along by the rider's feet. What it already had was the essential layout: two wheels in line and a steerable front wheel, which lets the rider balance by steering into a lean. That layout is the one still used today, which is why the machine is regarded as the ancestor of the bicycle (check).