On a sunny day, as the distance from your hand to the ground increases, the shadow of your hand on the ground become fuzzier because:

the Sun is a circle in the sky and that creates a penumbra

Explanation:

A penumbra is basically a lighter and hazy outer part of the shadow. It is the partially shaded portion of the outer region of a shadow that is cast by an opaque object.

In the context, as the distance from the hand to the surface of the ground increases on a sunny day, the shadow of the hand that falls on the ground becomes fuzzier because the sun is an opaque object in the sky and it creates a penumbra which makes the shadow of the hand on the ground fuzzier as the distance is increased.

the answer is definitely c.