Introduction:
When a body is projected from the ground obliquely, it follows a parabolic trajectory. During its downward motion, the body is influenced by the force of gravity. The power delivered by gravity to the body can be analyzed to understand its behavior.

Understanding Power:
Power is defined as the rate at which work is done or energy is transferred. Mathematically, power (P) can be calculated as the product of force (F) and velocity (v) - P = F * v. In the case of gravity, the force is the weight of the body (mg), where m is the mass of the body and g is the acceleration due to gravity.

Analysis of Power During Downward Motion:
During the downward motion of the body, the power delivered by gravity can be examined.

1. Initial Phase: As the body starts descending, the velocity is maximum and the power delivered by gravity is also maximum. This is because the force of gravity is acting in the same direction as the velocity, resulting in a larger magnitude of power.

2. Continued Descent: As time progresses, the body moves away from its initial projection point, and its velocity decreases due to the opposing force of gravity. Consequently, the power delivered by gravity also decreases. This is because the force of gravity acts against the direction of motion, reducing the magnitude of power.

3. Terminal Phase: Eventually, the body reaches its maximum height and starts descending towards the ground. At this point, the velocity becomes zero momentarily, and the power delivered by gravity is also zero. This is because there is no motion, and hence no work is being done.

4. Continued Descent Towards Ground: As the body descends further, the velocity starts increasing in the opposite direction. However, the magnitude of power delivered by gravity remains constant. This is because the force of gravity is acting against the direction of motion, but the magnitude of the force remains the same.

Conclusion:
In summary, during the downward motion of a body projected obliquely from the ground, the power delivered by gravity changes. Initially, it is at its maximum, then decreases, becomes zero at the highest point, and finally remains constant during the continued descent towards the ground. Therefore, the correct answer is option 4) first decreases and then becomes constant.

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