Question

This organism has mouth on its lower side and anus on upper side

• A. Limulus
• B. Buthus
• C. Daphnia
• D. Sea urchin

Answer 1

The correct option is D Sea urchin

A) $\text{Limulus}$ (king crab) is an arthropod that has a terminal mouth and its anus on the lower surface.

B) $\text{Buthus}$ (scorpion) is an arthropod that has a terminal mouth on its anterior end and an anus on its posterior end.

C) $\text{Daphnia}$ (water flea) is an arthropod. It's mouth is terminal and has mandibles for chewing.
D) The aboral surface (upper surface) of sea urchins bears the anus and the madreporite. The oral surface is the lower surface and bears the mouth.
So, the correct answer is 'Sea urchin'.