The correct answer is: D. At the Equator.
The Earth’s axis is tilted at an angle of 23.5 degrees relative to its orbital plane. This means that the Northern and Southern Hemispheres receive different amounts of sunlight at different times of the year. At the Equator, the sun is directly overhead at noon on the equinoxes (March 20 and September 22). This means that the days and nights are of equal length on these days.
At the Tropic of Cancer (23.5 degrees North latitude) and the Tropic of Capricorn (23.5 degrees South latitude), the sun is directly overhead at noon on the summer solstice (June 21 in the Northern Hemisphere and December 21 in the Southern Hemisphere). This means that the days are longer than the nights at these latitudes during the summer months.
At the North Pole and the South Pole, the sun does not rise above the horizon at all during the winter months and does not set below the horizon at all during the summer months. This means that the days are very short during the winter and very long during the summer.
In conclusion, the only place on Earth where the days and nights are of equal length all year long is at the Equator.