Which of the following types of UPS would be used with equipment that is very sensitive to power fluctuations?

An Offline / Standby UPS only switches to battery power when a power failure occurs, offering minimal protection against minor fluctuations and voltage sags/surges.

A Line interactive UPS can regulate voltage fluctuations without switching to battery by using an autotransformer, but it still passes raw utility power through during normal operation and has a transfer time to battery power.

Rackmount describes a physical form factor of a UPS, not its operational type or level of power protection.

An Online / Double Conversion UPS continuously converts incoming AC power to DC to charge its battery, and then converts DC power back to AC to power the connected equipment. This "double conversion" process ensures that the load always receives clean, conditioned power, regardless of the quality of the incoming utility power, making it ideal for sensitive equipment.