Which of the following characteristics is present in $Ascaris$?

While trying to find out the characteristics of a newly found animal,a researcher performed histology on the adult animal and observed a cavity with the presence of mesodermal tissue towards the body wall,but no mesodermal tissue was observed towards the alimentary canal. What could be the possible coelom of that animal?

$Ascaris$ completes its life cycle in

The animal in which sexes can be differentiated from external morphology is:

Infection of $Ascaris$ usually occurs by

The only phylum bearing pseudocoelom is