In a state machine, what happens when a composite state is active?

In a state machine, when a composite state is active, it is designed to contain multiple substates within it. The key characteristic of a composite state is that at any given moment, it can only have one of those substates active. This hierarchical structure allows for more complex behaviors while ensuring that the system remains in a well-defined state.

The active substate can transition to other substates or trigger events based on the defined state machine behavior. This design promotes clarity in state management, enabling actions to be compartmentalized within a single overarching state.

The other options do not accurately reflect how composite states function. For example, having all substates active simultaneously contradicts the fundamental principle of maintaining a single active state within the composite. Limiting the activity of substates or disallowing transitions while a composite state is active does not align with the intended functionality of a composite state within state machine modeling.