The correct answer is: B. the plane of the equator.
The equator is an imaginary line that divides the Earth into two hemispheres, the Northern Hemisphere and the Southern Hemisphere. It is located at 0 degrees latitude and is the longest line of latitude on Earth. The equator is also the only line of latitude that is not a parallel.
The International Date Line is an imaginary line that runs from the North Pole to the South Pole and separates two calendar days. It is located at 180 degrees longitude, halfway around the world from the Prime Meridian.
The Tropic of Cancer and the Tropic of Capricorn are two imaginary lines that run parallel to the equator. The Tropic of Cancer is located at 23.5 degrees north latitude, and the Tropic of Capricorn is located at 23.5 degrees south latitude. These lines mark the southernmost and northernmost latitudes at which the Sun can be directly overhead at noon.
I hope this helps!