They are brought from colder regions e.g. the North and South poles where ice caps are melting to give cold water. Currents are due to the effect of wind on the water.
An important tool in understanding the actual numerical dates of past geologic events is radioactivity.
The answer is D. Region.
It is NOT:
Latitude because it is the distance from the Earth's equator.
Place because that is just one location.
Longitude because it is the distance east and west from of the meridian at Greenwich, England.