Which of the following describes a blind spot?

A blind spot refers to an area surrounding a vehicle that cannot be seen by the driver through standard mirrors, such as the outside and rearview mirrors. This is particularly critical when changing lanes or merging, as vehicles or objects within this area may be entirely invisible to the driver.

The other options do not accurately depict the concept of a blind spot. The area seen in the rearview mirror is not a blind spot because it is perfectly visible to the driver. Similarly, the area that is directly in front of the vehicle is also not classified as a blind spot; this area is within the driver's line of sight. Lastly, the area visible in the side mirrors does not describe a blind spot, as side mirrors are intended to eliminate as much of the blind spot as possible and provide a clearer view of adjacent areas. Thus, the definition that it cannot be seen in the outside mirror(s) precisely captures the essence of what a blind spot is.