Question

the darkest part of a shadow is closest to what?
the light source
the object casting the shadow
the edge of the paper

Explanation:

In the context of shadows (a concept in Physics, a subfield of Natural Science), the darkest part of a shadow (umbra) is formed where the object blocks most light. This area is closest to the object casting the shadow, as the object's position determines the region with minimal light penetration. The light source is opposite in relation to the shadow's darkness gradient, and the edge of the paper is irrelevant to the shadow's darkness origin.

Answer:

B. the object casting the shadow