AGeoid
BEllipsoid
COblate Spheroid
DSpheroid
Answer:
A. Geoid
Read Explanation:
The Earth
Shape
For a long time the Earth was believed to be flat.
The concept of a spherical Earth was first put forward by the Greek philosopher Thales in the 7th century BCE. However, he believed that this sphere floated on water.
The Greek philosophers Pythagoras and Aristotle established that the Earth is spherical in shape. Copernicus strongly supported this concept
Aryabhata, the Indian astronomer strongly believed the shape of the Earth to be spherical and that it spins on its own imaginary axis. Years later Magellan's voyage round the world proved that the Earth is spherical.
Sir Issac Newton proved that the Earth is not truly spherical in shape, but slightly flattened at the poles and bulged in the middle.
The spherical shape of the Earth which is slightly flattened at the poles and bulged at the Equator is known as Geoid. The word Geoid means 'earth-shaped'.