The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
The tube within the tube
body plan It is found in higher animal groups from nematodes to chordates. The
body consists of two openings that is, one for ingestion and one for egestion.
Protostomes plan (Proto-first; stoma-mouth) found in non-chordates like flatworms, roundworms,
annelids, molluscs and arthropods. In this mouth is derived from the blastopore
of the embryo and anus is formed later. Deuterostomes plan It is found in
echinoderms, hemichordates and chordates. In this, the anus is derived from the
blastopore and mouth arises at the opposite end.
So, the correct answer is option A