Which of the following is an evidence for evolution, as observed by Karl Ernst von Baer?

Karl Ernst von Baer, a 19^th century embryologist, made important contributions to the understanding of evolution. He was the first to describe the similarities in the early embryonic development of different species, and he noted that embryos of different species show a remarkable similarity in their earliest stages of development. This observation provided evidence for the theory of evolution and supported the idea that all animals shared a common ancestor.