At what speed must a business car yield to entering traffic?

The correct answer indicates that a business car must yield to entering traffic at all times, regardless of speed limits. This approach aligns with the principle of ensuring safety on the road. Drivers must always prioritize yielding to oncoming traffic to prevent accidents, as they can be unpredictable. The context here is about the traffic flow and the need to maintain safe interactions between vehicles, especially when merging into lanes where other vehicles are present.

While the other choices suggest specifics or conditions under which a business car would yield, they do not encompass the complete traffic safety principle. The notion of varying speed limits or yielding based on specific speeds might lead drivers to misunderstand the fundamental rule of always yielding to oncoming traffic when merging or entering. This answer reinforces a broader understanding of traffic safety by emphasizing that the responsibility to yield is constant, regardless of speed or other conditions.