Which of the following was an economic spin off of the success of automobiles?

A. coal industry

B. motels

C. railroads

D. clothing stores

Answer: A. motels

An economic spin-off refers to a potential secondary economic effect from the implementation of a new project. In this case, motels were an economic spin-off because they were an unintended effect of automobiles. As the popularity of the car rose, people started using it as a method of transportation for long-distance travel. This meant that road trips became more common, and the need to stop and rest gave rise to motels.

Motels is the answer