The correct answer is option 1 - In the South Atlantic Ocean.

Option 1 refers to the geographical position of 0° latitude and 0° longitude. This position is known as the Prime Meridian and the Equator, where the lines of latitude and longitude intersect. While the other options may have some significance in relation to geographical features or locations, none of them accurately represent the position at 0° latitude and 0° longitude.

Option 2 - In the Mediterranean Sea, is incorrect because the Mediterranean Sea is not at the position of 0° latitude and 0° longitude.

Option 3 - In Ghana, a West African country, is incorrect because Ghana is located at approximately 7° latitude and 1° longitude, not at the position of 0° latitude and 0° longitude.

Option 4 - At Greenwich Observatory in England, is also incorrect. While Greenwich Observatory in England is a significant location in terms of measurements of longitude, it is located at approximately 51°28`38" N latitude and 0°00`00" E longitude, not at the position of 0° latitude and 0° longitude.

Hence, the correct answer is option 1 - In the South Atlantic Ocean.