What is the primary function of a Class V close-proximity curb mirror (pasqyra e trotuarit) mounted above the passenger-side door?

1. To reflect sunlight onto the passenger doorstep in winter
2. To check whether the fuel filler cap is locked
3. To show the ground area immediately adjacent to the passenger side of the cab, enabling the driver to see pedestrians, cyclists, and curbs
4. To look backwards along the left highway shoulder