Question 2004Navigation General

The correct answer is A) only one high and one low water occur during a lunar day. A diurnal tide is a type of tide where there is only one high tide and one low tide per lunar day (approximately 24 hours and 50 minutes). This is in contrast to a semi-diurnal tide, which has two high tides and two low tides per lunar day. The other options are incorrect because: B) two high tides in a lunar day would describe a semi-diurnal tide, not a diurnal tide; C) the high and low tides being exactly six hours apart is a characteristic of a semi-diurnal tide, not a diurnal tide; and D) the high and low tides being higher/lower than usual is not part of the definition of a diurnal tide.