Which of the following sleep modes is also known as Hibernation in Windows operating systems?

S3 (Suspend-to-RAM) is typically known as "Sleep" or "Standby" in Windows, where the system context is maintained in RAM, allowing for a quicker resume than hibernation.

S2 (Suspend-to-RAM, lower power) is a seldom-used ACPI state, typically superseded by S3, and is not known as Hibernation.

S4 is the ACPI (Advanced Configuration and Power Interface) global system state that corresponds to Hibernation in Windows, where the system's volatile memory contents are saved to persistent storage (like the hard drive) before the computer is powered off completely, allowing for a full power-off state with resume capability.

S1 (Power on Suspend) is a low-power ACPI state where the CPU stops executing instructions but is still powered, and RAM contents are maintained, but it's not hibernation.