California's Basic Speed Law says:

• A. You should never drive faster than is safe for current conditions.
• B. You should drive at the posted speed limit.
• C. You should drive at the flow of traffic.
• D. You should slow down in rain.

Answer: (A)

You must drive at a speed that is safe for the current conditions. California’s Basic Speed Law requires you to adjust your speed based on factors like weather, visibility, road surface, curves, hills, and the presence of other vehicles or pedestrians. The posted speed limit is a maximum for ideal conditions, not a guarantee of safety, so you may need to slow down when conditions are poor.

That’s why the correct idea is the one that says you should never drive faster than is safe for current conditions. Driving at the posted limit isn’t always safe, and simply following the flow of traffic isn’t enough if conditions require slower speeds. Slowing down only in rain misses the broader obligation to adjust speed for all hazardous conditions.