The correct answer is D. 1
A stability factor is a measure of how stable a system is. A system with a stability factor of 1 is perfectly stable, meaning that it will always return to its original state after being disturbed. A system with a stability factor of less than 1 is unstable, meaning that it will continue to diverge from its original state after being disturbed. A system with a stability factor of greater than 1 is metastable, meaning that it will eventually return to its original state after being disturbed, but it may take a long time to do so.
In the context of control systems, a stability factor of 1 is ideal because it means that the system will always return to its original state after being disturbed. This is important because it ensures that the system will continue to function properly even in the event of a disturbance.
The other options are incorrect because they do not represent ideal stability factors. A stability factor of 100 is too high, meaning that the system will be very sensitive to disturbances and will likely oscillate around its original state. A stability factor of 200 is even higher, meaning that the system will be even more sensitive to disturbances and will likely oscillate even more violently. A stability factor of more than 200 is not possible, because a system with a stability factor greater than 1 is metastable.