A city planner is using simulation software to study crowd flow out of a large arena after an event has ended. The arena is located in an urban city. Which of the following best describes a limitation of using a simulation for this purpose? A The model used by the simulation software cannot be modified once the simulation has been used. B The model used by the simulation software often omits details so that it is easier to implement. C Running a simulation requires more time to generate data from trials than observing the crowd exiting the arena at various events. D Running a simulation requires a large number of observations to be collected before it can be used to explore a problem.