What must be confirmed about the rearview mirrors during inspection?

The rearview mirrors must be operational and provide a clear view because they are essential for the safe operation of the vehicle. During an inspection, it's important to ensure that the mirrors not only can be adjusted to accommodate the driver's preferred line of sight but also that they deliver a clear and unobstructed view of the road and any surrounding traffic. This ensures that the driver can make informed decisions while driving, enhancing overall safety.

The other choices do not align with the safety standards required during inspections. For instance, adjustable but non-functional mirrors would not serve their purpose of providing visibility. Specifying a brand is irrelevant; safety standards are focused on the function and clarity of the mirrors rather than their manufacturer. Lastly, rearview mirrors are not optional as they play a critical role in ensuring the driver's visibility of what is behind and to the sides of the vehicle.