The acceleration due to gravity may vary with altitude and depth. Why does satellite need no fuel to go around a planet in its fixed orbit.

Choose the correct alternative: i)Acceleration due to gravity increases/decreases with increasing altitude. ii)Acceleration due to gravity increases/decreases with increasing depth. iii)The total energy of an orbiting satellite is negative of its kinetic/potential energy. iv)The polar satellite go around the earth in a north-south direction/east-west direction.

The acceleration of a body due to the force exerted by earth on it is known as acceleration due to gravity. Why does earth impart same acceleration on all bodies?