What should you do if a '20' shows up on the charger?

When a '20' appears on the charger, it signifies that there are 20 uses left before the battery needs to be recharged again. This is an important indicator for users regarding the remaining power available for operation, allowing them to plan for the next charging cycle proactively. Understanding this prompt helps in maintaining device functionality and ensuring that the user does not run out of power unexpectedly.

Option A, which suggests replacing the battery, is not relevant at this stage since the battery is still usable with 20 uses remaining. Option B, indicating a device malfunction, is incorrect because a '20' does not signify any fault; it simply indicates the battery status. Lastly, option D, which involves disassembling the device, is unnecessary and inappropriate when the device's operational status is confirmed as functional with remaining use capacity.