What facts implies that humans and fish had a common ancestor?

 the correct answer is option D). both species have gill slits when they are embryos.

Explanation:

A common ancestor of humans and fish denotes the most recent organism, from which both the humans and fish have been evolved. Humans and fishes are vertebrates, which possess spinal column or backbone. Along with this, human embryos also go through a stage, during which they have gill-slits like structures in their neck as present in fish embryos.

These structures do not found in mature humans like fishes, but they support the fact that the humans share a common ancestral organism with fish.