An animal devoid of anus is

The most efficient reproductive system is present in the animals of which phylum?

What are the peculiar features that you find in parasitic platyhelminthes?

The study of worms causing parasitic infestation in humans is known as:

Given below are two statements.
Statement $I$: Cephalic ganglion appears like $U$ shaped structure in Hydra.
Statement $II$: Ventral nerve cords are connected to each other by commissure in a ladder like manner in Planarian.
In the light of above statements,choose the most appropriate answer from the options given below:

In which of the following phyla is sexual dimorphism not observed?