The presence of gill-like slits in a human embryo is considered to be evidence for the

Out of the following given choices;

A. theory that fish and mammals have a common ancestry

B. theory that the first organisms on Earth were heterotrophs

C. close relationship between fish and mammalian reproductive patterns

D. close relationship between humans and annelids

The answer is A. Many embryos of the kingdom Animalia share similarities in the early stages depicting that they share a common ancestor. The gill slits is one example. They diverge in later stages to become Pharyngeal in the human embryo, while they differentiate into gills in fish.