A sign with a black background showing a straight line and a non-straight line indicates what?

Answer: D — No passing zone

The sign with a black background displaying a straight line alongside a non-straight line indicates a no-passing zone. This sign is placed in areas where overtaking or passing another vehicle is prohibited due to the potential for hazardous conditions, such as curves or intersections ahead where visibility may be limited. Such signs are crucial for ensuring safety on the road, as they help prevent accidents that may occur when drivers attempt to pass in situations where they cannot clearly see oncoming traffic. In South Dakota and many other jurisdictions, understanding and adhering to no-passing zone signs is essential for maintaining safety on the roads.