Concept:On March 21, the Sun is overhead at the Equator, causing an equinox. During an equinox, day and night are nearly equal everywhere on Earth.
Explanation:March 21 is the March equinox, called the vernal equinox in the Northern Hemisphere and the autumnal equinox in the Southern Hemisphere.
On this date, the direct rays of the Sun fall vertically on the Equator.
The circle of illumination extends exactly through the North Pole and the South Pole.
This circle cuts every parallel of latitude into two equal halves.
Therefore, all towns in the Southern Hemisphere receive about
12 hours of daylight and
12 hours of darkness.
Thus, day and night have equal lengths on this day.
Answer:D. equal lengths of day and night