The life span of $Ascaris$ is:

In $Ascaris$,the $3^{rd}$ moulting takes place in:

In the given figure,what does the part labeled '$a$' represent?

The $Tube-within-a-Tube$ body plan is shown by:

Which of the following is true for $Ascaris$?

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?