Final answer:
The error is saying that electrons travel at the speed of light when in reality they move much slower, with a drift velocity much less than the speed of light.
Step-by-step explanation:
The error in saying that electrons in common battery-driven circuits travel at about the same speed of light is that electrons actually travel much slower than light. This is represented by the letter C) Electrons travel much slower than light. In conducting wires, electrons move in a zig-zag fashion due to their interactions with atoms and other free electrons, resulting in a drift velocity, which is significantly slower than light's speed. While electrical signals can move at speeds up to the order of 108 m/s, the electrons themselves typically drift at speeds around 10-4 m/s, demonstrating the vast difference between signal propagation and actual electron motion in a conductor.