Final answer:
When approaching your vehicle, the step that is not necessary is to start the engine immediately. It's important to check the interior and surroundings for safety reasons, while verifying the vehicle's registration is something you do periodically, not each time you approach to drive.
Step-by-step explanation:
When approaching your vehicle, there are several necessary steps to ensure your safety before you start driving. One of the necessary steps is to check the back seat and interior (option a) for your personal safety to ensure no one is hiding in the vehicle. Another necessary precaution is to look around for any suspicious activity (option c), which can help you avoid potential dangers or threats. However, verifying the vehicle's registration (option b) is not a step you need to take every time you approach your vehicle to drive; rather, it should be done periodically to ensure the documentation is up-to-date and adheres to legal requirements. Therefore, starting the engine immediately (option d) is the task that is NOT a necessary step when approaching your vehicle, as it is important to conduct other checks and preparations before commencing to drive.