In the life history of the liver fluke,the following stages are present: $(1)$ Cercaria,$(2)$ Metacercaria,$(3)$ Sporocyst,$(4)$ Redia,$(5)$ Miracidium. What is their proper sequence?

Animals of which phylum have hooks and suckers and are endoparasites on other animals?

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:

The 'tube-within-a-tube' body plan is not present in the:

Which of the following phyla lacks a coelom?

The $Cysticercus$ larva of $Taenia$ $solium$ develops in: