Option 1: The Arctic Circle is a circle of latitude that is located at approximately 66.5 degrees north of the Equator. It marks the southernmost point at which the sun can remain continuously below or above the horizon for 24 hours during the summer and winter solstices, respectively. However, it is not the greatest circle.

Option 2: The Equator is a circle of latitude that is located at 0 degrees and divides the Earth into the Northern Hemisphere and the Southern Hemisphere. It is the longest circle of latitude and represents the halfway point between the North Pole and the South Pole.

Option 3: The Tropic of Cancer is a circle of latitude that is located at approximately 23.5 degrees north of the Equator. It marks the northernmost point at which the sun can be directly overhead at noon during the summer solstice in the Northern Hemisphere.

Option 4: The Tropic of Capricorn is a circle of latitude that is located at approximately 23.5 degrees south of the Equator. It marks the southernmost point at which the sun can be directly overhead at noon during the summer solstice in the Southern Hemisphere.

The correct answer is option 2, the Equator. It is the greatest circle as it