In the filarial worm $(Wuchereria \text{ } bancrofti)$, which of the following statements is true regarding their size?

Roundworms differ from flatworms in having a

The cross-section of an animal body is given below:
Which of the following animals will satisfy the above cross-section?

Pineal setae in male $Ascaris$ are found in

Syncytial epidermis is present in

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?