Question

mammals are classified as deuterostomes where the blastopore develops into the
anus
mouth

Explanation:

Deuterostomes are a group of animals. In deuterostomes, during embryonic development, the blastopore (the opening of the archenteron) develops into the anus. Mammals are deuterostomes. In protostomes, the blastopore develops into the mouth.

Answer:

anus