That's an incorrect answer. A light-day means "the distance covered by the speed of light in a day (24h)". The day length is related to Earth's turn speed, it's not related to its distance to the sun.
> And I wonder if “one light-day” would even be accepted as an answer.
Absolutely not. First, a light-day is a distance, not a unit of time. Second, Voyager 1 is almost 1 light day from the sun. The earth is approximately 0.5% of a light-day from the sun.
