Final answer:
Before selling a cell phone, you should backup your data and remove the SIM card to protect personal information and prevent loss of important files.
Step-by-step explanation:
Before selling your cell phone, two important things you should consider are: a. Backup your data and d. Remove the SIM card. Backing up your data ensures that you do not lose important information such as contacts, photos, and messages. Removing the SIM card is crucial for protecting your personal information and preventing the next user from having access to your phone number and potentially your billing information.
While options b. Wipe the device and c. Check the market value are also important steps to take before selling your phone, they were not listed as the choices for the two considerations to be addressed according to the question.