B
In jurisdictions where use of headlights is optional when visibility is good, drivers who use headlights at all times are less likely to be involved in a collision than are drivers who use headlights only when visibility is poor. Yet Highway Safety Department records show that making use of headlights mandatory at all times does nothing to reduce the overall number of collisions. Which one of the following, if true, most helps to resolve the apparent discrepancy in the information above?
A: In jurisdictions where use of headlights is optional when visibility is good, one driver in four uses headlights for daytime driving in good weather.
B: Only very careful drivers use headlights when their use is not legally required.
C: The jurisdictions where use of headlights is mandatory at all times are those where daytime visibility is frequently poor.
D: A law making use of headlights mandatory at all times is not especially difficult to enforce.