The right answer is Positive feedback.
Feedback is the return action of an effect on the origin of the latter: the sequence of causes and effects thus forms a loop called a feedback loop.
There are many types of feedback:
* Positive feedback amplifies the deviations with the stable state, the system is self-powered, for example in the case of an explosion.
* Negative feedback tends to reduce deviations and causes damping that allows regulation.
* Neutral feedback makes no changes to the system.