Which of the following phyla is the first to exhibit organ-level organization?

Identify the given animal and its habitat.

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:

Which structure is found in the phylum Platyhelminthes to attach to the host?

Which of the following is the free-swimming ciliated larval stage of the Liver Fluke ($Fasciola$ $hepatica$)?

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