A white painted curb means:

Answer: D — Loading zone for passengers or mail only.

Curb color shows when you can stop and why you’re stopping. A white painted curb means you may stop briefly to load or unload, but only for passengers or mail. You should not park there or leave the vehicle unattended—stop just long enough to drop off or pick up and then pull away. So this is why the statement about a white curb fits: it’s a designated loading zone for passengers or mail only, not a general parking spot or a bus stop, and not a long-term parking area. The other scenarios describe conditions that aren’t allowed or aren’t the purpose of a white curb.