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

Definition:
A machine is a device that consists of a combination of moving parts (links and pairs) designed to transmit force and motion to perform work. A structure, on the other hand, is a stationary system of connected elements that supports loads without transmitting motion.

Correct Answer: Option D – All of the above

Explanation:
The distinction between a machine and a structure can be understood by analyzing several fundamental differences:

1. Relative Motion:
In a machine, the parts move relative to one another to perform a function. These relative motions are essential for the machine's operation.
In a structure, there is no relative motion between the connected members; they remain in fixed positions relative to each other to bear loads.
This supports Option A.

2. Transmission of Power and Motion:
In a machine, links are used to transmit both power and motion between components to produce mechanical work.
In contrast, a structure’s members only transmit forces (tensile or compressive) to maintain equilibrium without generating motion.
This validates Option B.

3. Energy Transformation:
A machine is specifically designed to transform energy into useful work by means of mechanical processes (e.g., engines, pumps).
In a structure, there is no transformation of energy into work; instead, the goal is to remain stable under applied loads.
This confirms Option C.

Since all three statements are accurate descriptions of the difference between a machine and a structure,

Conclusion:
The correct answer is Option D – All of the above.