Final answer:
When driving, it is critical to check traffic behind you whenever you intend to change lanes to ensure road safety and prevent accidents.
Step-by-step explanation:
The correct answer to the question is c) Intend to change lanes. It's important to always check traffic behind you when you plan on changing lanes. This is because you need to ensure that there is enough space for your vehicle and that it is safe to make the lane change without risking a collision. Safety on the road is paramount, and making sure you are aware of your surroundings is a key part of driving safely.
While options a) Want to race with other vehicles and b) Need to adjust your radio are not safe driving practices and should be avoided, and d) Are driving in a straight line doesn't specify a situation where a lane change or similar maneuver would necessitate checking the traffic behind, therefore it is less critical compared to changing lanes.