Final answer:
Human embryos having a tail is an example of (Option c) embryonic development as evidence of evolution, showcasing conservation of certain features in embryonic forms across various species.
Step-by-step explanation:
The example of human embryos having a tail at one point during development is an evidence of embryonic development in the study of evolution. This embryology provides insight into the relatedness of various species and their shared ancestry. It demonstrates that structures which may not be present in the adult form, such as a tail in humans, often appear during the embryonic stages of development. This is due to evolutionary changes where remnants of ancestral features can be observed in the early development stages of descendants but are lost before reaching adulthood. Embryonic development is crucial in understanding the evolutionary process and the conserved elements across different species.