Which of the following statement is correct as regard to the difference between a machine and a structure?

A. The parts of a machine move relative to one another, whereas the members of a structure do not move relative to one another

B. The links of a machine may transmit both power and motion, whereas the members of a structure transmit forces only

C. A machine transforms the available energy into some useful work, whereas in a structure no energy is transformed into useful work

D. All of the above

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