What does a white painted curb indicate?

Answer: B — Loading zone for passengers or mail only

A white painted curb indicates a loading zone specifically for passengers or mail only. This designation is meant to facilitate quick loading and unloading without the need for long-term parking. The presence of a white curb allows drivers to pull over temporarily to pick up or drop off passengers or to handle mail services without significantly hindering traffic flow. In contrast, a loading zone for freight or passengers suggests that more extensive stops may be allowed for loading and unloading purposes, which is not the case with a white curb. This distinction is important for ensuring that the traffic regulations are followed, as it helps define areas where stopping is permitted without causing congestion or safety issues for other road users.