Option-1 states that both statements are individually true and Statement II is the correct explanation of Statement I.

Let`s analyze each statement separately:

Statement I: A body weighs less on a hilltop than on Earth`s surface even though its mass remains unchanged.

This statement is true. When we say that a body weighs less on a hilltop, it means that the force of gravity acting on the body is less compared to when it is on Earth`s surface. Weight is the force experienced by an object due to gravity, and it is directly proportional to the acceleration due to gravity. Since gravity decreases with height, the weight of an object decreases as it moves higher, even though its mass remains the same.

Statement II: The acceleration due to gravity of the Earth decreases with height.

This statement is also true. The acceleration due to gravity is not constant throughout the Earth. As we move farther away from the Earth`s center, the gravitational force decreases. This is because the Earth`s mass is concentrated towards its center. Consequently, the acceleration due to gravity decreases as we move higher, hence validating Statement I.

Therefore, Option-1 is the correct answer as both statements are individually true, and Statement II explains why Statement I is true.