After You've Backed Up Your Data to Your New Phone

Multiple Choice

After you've backed up your data to your new phone, how can you securely delete the data from your old phone before donating it to a charity for reuse?

A) Reset the device to its factory settings.
B) Delete each file off the old phone, one by one.
C) Dispose of the old battery.
D) Back up the old phone to the cloud.