Explanation:

Scanned keyboard with N-key rollover:
In a scanned keyboard with N-key rollover, the debounce circuit waits for 2 keyboard scans and then checks whether the key is still depressed. N-key rollover refers to the ability of a keyboard to register multiple key presses simultaneously. This means that when multiple keys are pressed, each key is individually recognized by the keyboard controller.

Debounce circuit:
A debounce circuit is used to eliminate the possibility of multiple inputs being registered due to mechanical bouncing of the key switch contacts. When a key is pressed, the switch contacts may bounce multiple times before settling into a stable state. The debounce circuit filters out these bounces and ensures that only a single key press is registered.

Working of the debounce circuit:
The debounce circuit typically works by waiting for a certain amount of time after a key press before checking the state of the key. This waiting period allows for the switch contacts to settle down and ensures that only a single key press is registered.

Scanned keyboard mode:
In a scanned keyboard mode, the keyboard controller scans the keys in a systematic manner to detect any key presses. It sequentially checks each key to see if it is depressed or not.

Key lockout:
Key lockout refers to the situation where a key press is ignored if another key is already pressed. This is typically done to prevent accidental key presses when multiple keys are pressed simultaneously.

Explanation:
In this scenario, the debounce circuit waits for 2 keyboard scans before checking whether the key is still depressed. This is done to ensure that the key press is stable and not a result of bouncing contacts. In scanned keyboard mode with N-key rollover, the keyboard controller can detect multiple key presses simultaneously. By waiting for 2 keyboard scans, the debounce circuit ensures that the key press is stable and not a result of bouncing contacts. This helps in accurately detecting the key presses and preventing multiple inputs from being registered.

Therefore, option B is the correct answer as it describes the scenario where the debounce circuit waits for 2 keyboard scans in a scanned keyboard mode with N-key rollover.