Which of the following is an acoelomate animal with a protandrous nature?

Assertion $A$: Animals of Phylum $Platyhelminthes$ have an incomplete digestive tract.
Reason $R$: In $Platyhelminthes$,the digestive tract opens to the outside through a single opening.
Which option is correct for Assertion $A$ and Reason $R$?

Both alternation of generations and alternation of hosts are present in

Write the general features of flatworms.

Rostellum and hooks are absent in the scolex of

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?