A

To determine the acceleration due to gravity 'g' on the surface of the Earth, we use the formula derived from Newton's law of gravitation, which states that the gravitational force 'F' acting on a body of mass 'm' is given by:
$$ F = \frac{GMm}{R^2} $$
where:
- G is the universal gravitational constant
- M is the mass of the Earth
- R is the radius of the Earth

The acceleration due to gravity 'g' is defined as the force per unit mass, i.e.,
$$ g = \frac{F}{m} = \frac{GM}{R^2} $$
This shows that 'g' is directly proportional to the mass of the Earth (M) and inversely proportional to the square of the radius of the Earth (R), confirming that 'g' is proportional to \( \frac{M}{R^2} \).
Therefore, the answer is represented in Option A.