Charlie wants to build a magnetic levitation train for his younger brother. Charlie has drawn a diagram of his train and has built the train. What should Charlie do next with his design?
A. Test the device, get feedback from other people, and revise the design if needed.
B. Show his design to other people and get feedback before selling his design.
C. Publish his design in a magazine as is and wait for investors.
D. Test the device and sell it to the local veterinarian.
