What is an objects center of gravity A) the exact center of its mass
B) the part that is closest to earth
C) any part of an object , as long as it has mass
D) all of the above

The Center of gravity is the average location of the weight of an object. We can completely describe the motion of any object through space in terms of the translation of the center of gravity of the object from one place to another, and the rotation of the object about its center of gravity if it is free to rotate. So the Answer is C.