Final answer:
François Arago experimentally verified the bright spot in a shadow with coherent light, confirming Augustin-Jean Fresnel's wave theory of light, whereas Thomas Young had earlier demonstrated light's wave nature through his double-slit experiment. Option d is the answer.
Step-by-step explanation:
The scientist who experimentally proved that a shadow of a circular object illuminated with coherent light would have a central bright spot, known as Poisson's spot, was François Arago. Augustin-Jean Fresnel had earlier predicted this effect as a consequence of the diffraction of light waves. Siméon-Denis Poisson was skeptical of Fresnel's wave theory and attempted to disprove it, but instead, Arago's experimental verification of the bright spot confirmed the wave nature of light. Earlier, Thomas Young had established the wave theory of light through his famous double-slit experiment, showing light’s interference pattern, which waves can create.