What is it called when the system and all the components except for the real-time clock are powered down

The correct answer to the following question will be "Mechanical off mode".

Explanation:

The device will appear to be either on or off to the user. No other states are measurable. The device does, however, support various power states that suit the power states specified in the ACPI specification. Such states also differ, like hybrid sleep and rapid startup. This subject discusses certain states and how they will be represented. The system is completely off, and no power is used. Only after a full reboot will the machine return to working condition. It is called mechanical off mode when the machine and all parts, except for the actual-time clock, are down powered.

Therefore, Mechanical off mode is the right answer.