What is caused by very low resistance and results in a slow transient response?

The phenomenon described in the question refers to a condition where very low resistance in a system causes a delayed response to changes in input, which is characteristic of over-damping.

In electrical circuits and systems, damping describes how oscillations in a system decay after a disturbance. When a system is over-damped, the resistance is so high relative to the inductance and capacitance that the system returns to equilibrium slowly without oscillating. This results in a smooth but prolonged response to changes, leading to a slow transient response due to the high level of resistance.

In contrast, under-damping would produce oscillations with a faster return to equilibrium, and critical damping is the optimal condition for the fastest return to equilibrium without oscillation. Regular damping is a less commonly defined term in this context and does not specifically apply to the relationship between resistance and transient response in a way that is as clear as over-damping does.

Therefore, over-damping is aligned with the characteristics of very low resistance leading to a slow response, making it the correct answer.