Question

why do a chicken embryo and a cow embryo look very similar even though the adults do not?
they are not related, but still have similar development.
they are distantly related, so their development is similar.
the embryos mutate in utero to form different structures.
the genetic makeup of the two species changes during development.

Explanation:

Chicken and cow are distantly - related species in the broader context of vertebrates. Their similar embryonic appearance is due to shared evolutionary history and common developmental pathways that have been conserved over time. As development progresses, species - specific traits become more pronounced.

Answer:

They are distantly related, so their development is similar.