D it is a simplification of a more complex phenomena that captures some aspects and leaves out others.
A simulation is considered an abstraction because it simplifies a more complex real-world system by only capturing certain aspects of it and leaving out others. This allows for a more manageable and tractable model of the system, but it is important to keep in mind that the simulation is not an exact representation of the real-world system. The other options (a, b, c) all describe features or elements of a simulation but do not explain why it is considered an abstraction.