The correct option is A Archenteron
Archenteron is the tube formed during gastrulation by means of invagination of the blastula wall inside the blastocele. It is the origin of the gastrointestinal tract. Blastopore is the opening of the archenteron to the exterior. Blastopore gives birth to one of the extremities of the digestive tube, the mouth of the protostome and anus in deuterostome.