Which iPhone setting should you choose to restore iPhone to factory settings?

To return an iPhone to factory settings from the device itself, use Erase All Content and Settings. Apple places this option under Settings > General > Transfer or Reset iPhone. It removes the user’s personal information, apps, and settings and returns the device to the setup state, so option A is correct. Reset All Settings is different: it returns many system settings to their defaults but does not erase personal data, apps, photos, messages, or documents. “Device Wipe” is not the user-facing iPhone setting used for a local factory reset, and Return to Service is a managed-device workflow rather than the standard Settings option for an individual user. Therefore, Erase All Content and Settings is the appropriate selection when the requirement is to restore the iPhone to factory settings.

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