I would go with B) Nerves in the finger detect stimuli and send the message to the brain.
In the case of liquid droplets, including water, surface tension is the factor, which is accountable for their shapes and configuration. Though can easily be malformed, the droplets of water seem to be pulled into a spherical shape due to the cohesive forces of the surface layer.
In the non-existence of other forces, involving gravity, the drops of almost all the liquids would be almost spherical.
they deleted my link but if u google this theres a pdf that should help
Answer:
the shadows are called umbra and penumbra
