Final answer:
A black arrow on a yellow sign curving to the left is a warning that the road ahead curves in that direction, signaling drivers to follow the curve and proceed with caution.
Step-by-step explanation:
When you see a black arrow on a yellow sign curving to the left, it means that the road ahead curves to the left, and you should prepare to follow that curve. This does not necessarily instruct you to make a left turn at an intersection; rather, it is a warning sign indicating that the road itself is going to change direction. You should reduce your speed if necessary and be aware of the road conditions as you continue driving.