What is a major characteristic of a 'simple' system?

A major characteristic of a 'simple' system is that it is a whole consisting of interacting parts. In systems engineering, a simple system can typically be characterized by the fact that its components work together in a defined manner to accomplish a specific function or purpose. Even if the system is described as 'simple,' the interaction between its parts is essential, as these interactions contribute to the overall behavior and functionality of the system.

For example, consider a basic mechanical clock as a simple system. It has various interacting parts like gears and springs, which work together to keep time accurately. This illustrates that even simple systems are not merely collections of components, but they exhibit a cohesive operation through their interactions.

The other options present concepts that do not accurately capture the essence of a simple system. A fixed component suggests a lack of interaction, while multiple independent elements imply a more complex or fragmented system. The notion that a simple system is theoretical and has no practical execution is not aligned with how simple systems function in practice; they exist and operate within real-world contexts.