The act of checking your blind spot before changing lanes is considered:

Answer: B — good driving habit.

Checking your blind spot before changing lanes is a crucial aspect of safe driving and is considered a good driving habit. This practice helps ensure that there are no vehicles, cyclists, or pedestrians in the areas that are not visible through your mirrors. Rearview and side mirrors provide a view of the traffic behind and alongside you, but they cannot capture everything due to the blind spots created by the vehicle's structure. By physically turning your head to check the blind spot, you actively enhance your awareness of your surroundings, which significantly reduces the risk of collisions when merging or changing lanes. This habit is an essential part of defensive driving, promoting both your safety and that of other road users. Engaging in this practice demonstrates a conscientious approach to driving, where you take extra steps to ensure that you are making informed decisions on the road.