The correct answer is D) about 50 minutes longer than the solar day. The lunar or tidal day is the period of time between two successive upper transits of the moon over a given location, and it is approximately 24 hours and 50 minutes long. This is because the moon takes slightly longer than 24 hours to complete one full rotation around the Earth, resulting in the lunar day being longer than the solar day. The other options are incorrect because: A) the lunar day is not the same length as the solar day, B) the lunar day is not about 10 minutes longer than the solar day, and C) the lunar day is not about 50 minutes shorter than the solar day.