Answer:
It should be the Prime Meridian.
Step-by-step explanation:
You do not have a picture but the equator is a line of latitude that travels east to west. The International Date line is an imaginary line through the Pacific Ocean that begins a new day (it has to do with time zones). The Arctic Circle is only in the north and it is a circle, not a line. Lastly, the prime Meridian is a line of longitude that travels from north to south and cuts the world in half between eastern and western hemispheres, like the Equator cuts the globe into the northern and southern hemispheres. The Prime Meridian goes through the Atlantic Ocean and cuts off put of Africa.
I hope this helps!